Charge Control Solenoid/Valve Question
05-22-06, 10:27 AM
#1
Junior Member
Thread Starter
Charge Control Solenoid/Valve Question
Hi all, I feel an essay coming on! Please bear with me, im trying to give you all the possible info i can, in the hope that it might "help those who help me".
I'm tring to fix a recurrent problem I have with my FD. The car will drive ok for 2/3 weeks, then i will get error code 45 on my ECU (charge control solenoid), in addition to error code 51 (high speed fuel pump relay), and the car will go into limp mode. I can clear the code (although the code is very persistent and a PITA to clear for some reason, even though I follow the procedure detailed in the user manuals, i.e. disconnect -ve batt terminal, foot on break...).
At a first glance i would guess error code 51 is a result of the car being in limp mode (ECU not engaging high speed fuel pump relay) so, if appropriate, i can ignore this for the time being and concentrate on my primary problem, the charge control solenoid error.
In my first year of owning the car, i came across this problem maybe 5 times in a whole year. Straight after starting the car, it would go into limp mode, I would shut the car down, come back to it half-day later and all would be fine with it. I did not have to clear any error codes or do anything for that matter... just wait...
Now, recently its become more of a pain. As i said i get it now once every 2/3 weeks, it requires me to manually remove the error code from the ECU to get the car out of limp mode, and even then, the code is VERY persistent...
Recently (the day before the problems started appearing regularly in-fact). I had some exhaust work done to the car:
- Replaced the HKS super dragger muffler with a generic hi-flow straight through muffler (the hks had completely collapsed
- Replaced my hollowed-out cat with a high-flow cat
I immediately noticed the car was overboosting. I had a perfect 10-8-10 pattern prior to the work, but after the work, my car peaks at 13 psi. I had the car dyno'd and I was told that the car is pumping enough fuel at higher boost to keep my air/fuel mixture in the safe zone, but I guess it might be playing havoc with my ECU's idea of 'how the world should be'...
Since replacing the rear muffler (3 way bend hks) with a straight-through item, I have realised this may be the cause of my over-boosting. It is my understanding that the wasting of excess boost is controlled by statically-mapped cycles of the Wastegate control solenoid, and this process relies on a known constant back-pressure of the exhaust. Once this exhaust pressure is changed, the boost control process is effected.
In order to understand/fix my problem, i guess i first need to properly understand a) What does the charge control solenoid do? and b) How does it do it (is it a duty cycled solenoid?) ? How is the error code 45 stored/checked (is it stored in persistent memory if it fails once, or is the solenoid polled/checked for a test-resistance each time i turn the ignition on to make sure it is ok)? For some reason i thought the charge control solenoid was linked to boost control, but upon studying the vaccum diagrams, it appears the Wastgate Control Solenoid is doing this job already?
As a first step, I've attempted to check the Charge Control Solenoid and the continuity of the wiring to it. I unplugged the ECU, put a multi-meter across the two wires from the charge control solenoid, and from memory, found the resistance to be 580-600 odd ohms. I compared this to readings from the other solenoids (there are a couple of others that are the same type) and these all appeared to be in that range.
The solenoid is mechanically/electrically a pretty simple thing, so i guess if i didnt see an open/short line, that would look pretty promising for it not being faulty (or being intermittently faulty - if it was perminantly fauly i wouldnt be able to remove the car form limp mode id suspect). If it was the case that the solenoid is ok, this might mean either the computer is in error (seeing the solenoid as faulty when it isnt), OR more likely, the solenoid is acting un-expectedly during operation and this is causing the fault to be logged.
So if the solenoid is behaving in an un-expected manner, what could be causing it?
Here are some scenarios ive been throwing around in my head:
1) New exhaust system causes car to overboost, ECU somehow senses the car is overboosting (map sensor?), ECU deduces the charge control solenoid is not operating properly (OR ECU attempts to run the duty controlled Charge control solenoid at 100% duty to cope with overboost), ECU logs a fault for the charge control solenoid, and puts the car into limp mode. Car in limp mode causes error code 51 to also appear when ECU prevents high speed fuel pump relay from coming online.
2) Charge Control Solenoid is actually intermittently/constantly broken
3) ECU is in error (not overly likely...)
I could go through the process of changing parts (charge control solenoid, exhaust, computer, etc), but I dont think this is a very good way to start out solving my problem. I would like to take a somewhat rational approach to it, or ill end up short on cash, and with a lot of work ahed of me ;-)
Quite possibly the longest post on rx7club.com? Thanks for any help you guys/gals can give me!
Sco.
I'm tring to fix a recurrent problem I have with my FD. The car will drive ok for 2/3 weeks, then i will get error code 45 on my ECU (charge control solenoid), in addition to error code 51 (high speed fuel pump relay), and the car will go into limp mode. I can clear the code (although the code is very persistent and a PITA to clear for some reason, even though I follow the procedure detailed in the user manuals, i.e. disconnect -ve batt terminal, foot on break...).
At a first glance i would guess error code 51 is a result of the car being in limp mode (ECU not engaging high speed fuel pump relay) so, if appropriate, i can ignore this for the time being and concentrate on my primary problem, the charge control solenoid error.
In my first year of owning the car, i came across this problem maybe 5 times in a whole year. Straight after starting the car, it would go into limp mode, I would shut the car down, come back to it half-day later and all would be fine with it. I did not have to clear any error codes or do anything for that matter... just wait...
Now, recently its become more of a pain. As i said i get it now once every 2/3 weeks, it requires me to manually remove the error code from the ECU to get the car out of limp mode, and even then, the code is VERY persistent...
Recently (the day before the problems started appearing regularly in-fact). I had some exhaust work done to the car:
- Replaced the HKS super dragger muffler with a generic hi-flow straight through muffler (the hks had completely collapsed
- Replaced my hollowed-out cat with a high-flow cat
I immediately noticed the car was overboosting. I had a perfect 10-8-10 pattern prior to the work, but after the work, my car peaks at 13 psi. I had the car dyno'd and I was told that the car is pumping enough fuel at higher boost to keep my air/fuel mixture in the safe zone, but I guess it might be playing havoc with my ECU's idea of 'how the world should be'...
Since replacing the rear muffler (3 way bend hks) with a straight-through item, I have realised this may be the cause of my over-boosting. It is my understanding that the wasting of excess boost is controlled by statically-mapped cycles of the Wastegate control solenoid, and this process relies on a known constant back-pressure of the exhaust. Once this exhaust pressure is changed, the boost control process is effected.
In order to understand/fix my problem, i guess i first need to properly understand a) What does the charge control solenoid do? and b) How does it do it (is it a duty cycled solenoid?) ? How is the error code 45 stored/checked (is it stored in persistent memory if it fails once, or is the solenoid polled/checked for a test-resistance each time i turn the ignition on to make sure it is ok)? For some reason i thought the charge control solenoid was linked to boost control, but upon studying the vaccum diagrams, it appears the Wastgate Control Solenoid is doing this job already?
As a first step, I've attempted to check the Charge Control Solenoid and the continuity of the wiring to it. I unplugged the ECU, put a multi-meter across the two wires from the charge control solenoid, and from memory, found the resistance to be 580-600 odd ohms. I compared this to readings from the other solenoids (there are a couple of others that are the same type) and these all appeared to be in that range.
The solenoid is mechanically/electrically a pretty simple thing, so i guess if i didnt see an open/short line, that would look pretty promising for it not being faulty (or being intermittently faulty - if it was perminantly fauly i wouldnt be able to remove the car form limp mode id suspect). If it was the case that the solenoid is ok, this might mean either the computer is in error (seeing the solenoid as faulty when it isnt), OR more likely, the solenoid is acting un-expectedly during operation and this is causing the fault to be logged.
So if the solenoid is behaving in an un-expected manner, what could be causing it?
Here are some scenarios ive been throwing around in my head:
1) New exhaust system causes car to overboost, ECU somehow senses the car is overboosting (map sensor?), ECU deduces the charge control solenoid is not operating properly (OR ECU attempts to run the duty controlled Charge control solenoid at 100% duty to cope with overboost), ECU logs a fault for the charge control solenoid, and puts the car into limp mode. Car in limp mode causes error code 51 to also appear when ECU prevents high speed fuel pump relay from coming online.
2) Charge Control Solenoid is actually intermittently/constantly broken
3) ECU is in error (not overly likely...)
I could go through the process of changing parts (charge control solenoid, exhaust, computer, etc), but I dont think this is a very good way to start out solving my problem. I would like to take a somewhat rational approach to it, or ill end up short on cash, and with a lot of work ahed of me ;-)
Quite possibly the longest post on rx7club.com? Thanks for any help you guys/gals can give me!
Sco.
The following users liked this post:
__swiller (07-18-20)
05-22-06, 11:31 AM
#2
These issues appear to be entirely separate in nature - their only common elements are the main relay, wiring harnesses, and the ECU. I think you should clear the codes, and if you can get the car running for a while, check for codes before the problem arises. Then see if there are any stored codes. I believe the 45 (CC Solenoid) is a ghost code that will post to memory but not trip the CEL. I would troubleshoot both issues, but I believe they are separate unless they always appear at exactly the same time.
Regarding your CC questions:
a) The charge control solenoid operates the charge control actuator (CCA). The CCA opens the passage for secondary charge to join the primary charge and on toward the engine. The occurs consistently at 4500rpm.
b) It is not a duty controlled solenoid. It flips at 4500 and stays that way as long as you're under heavy load.
Error code 45 is triggered when the ECU detects either an open circuit or short circuit (low resistance) on the CC solenoid circuit. The only two items on this path is the main relay and the CC solenoid. In some cases, heat causes the coil inside the solenoid to intermittently short or open, so the first thing to consider is testing the resistance of the solenoid both cold and hot (I use an oven at 90C to warm the solenoid for several minutes). If the electrical internals of the solenoid are good, you should see the resistance of the coil increase and that is all. (from around 38Ohms to 50-75Ohms when hot).
Other possibilities are a bad connection in one of the wiring harnesses, bad ECU, or a bad main relay. The harness(es) are the most likely of these alternative causes, and most expensive.
Regarding your scenarios:
1) CC solenoid is not a duty cycling solenoid, and to my knowledge it will not jump to limp mode when this solenoid is faulty. You will only get a code and troublesome boost above 4500rpm.
2) First/foremost route I would follow.
3) If the harnesses and solenoid check out, borrow another ECU for a quick test.
Onto code 51 / limp mode issue, which to my knowledge is entirely separate from a solenoid failure.
Have you replaced the fuel pump relays? (Maybe you can switch them with identical relays from a non-essential system just as a test, or borrow some known-good relays). If the relays are good, then if you have a multimeter and long test wires, you can manuall check the circuit when the ECU posts the code. Shake the wiring to see if it might be an intermittent short or open circuit. At this point using the wiring diagram (see the sticky thread at the top of this forum) to look for where this path appears at harness connectors and resume verifying each section of the path until you can isolate the bad harness. (Then if you confirm you have a bad harness, cry about the replacement cost).
Dave
Regarding your CC questions:
a) The charge control solenoid operates the charge control actuator (CCA). The CCA opens the passage for secondary charge to join the primary charge and on toward the engine. The occurs consistently at 4500rpm.
b) It is not a duty controlled solenoid. It flips at 4500 and stays that way as long as you're under heavy load.
Error code 45 is triggered when the ECU detects either an open circuit or short circuit (low resistance) on the CC solenoid circuit. The only two items on this path is the main relay and the CC solenoid. In some cases, heat causes the coil inside the solenoid to intermittently short or open, so the first thing to consider is testing the resistance of the solenoid both cold and hot (I use an oven at 90C to warm the solenoid for several minutes). If the electrical internals of the solenoid are good, you should see the resistance of the coil increase and that is all. (from around 38Ohms to 50-75Ohms when hot).
Other possibilities are a bad connection in one of the wiring harnesses, bad ECU, or a bad main relay. The harness(es) are the most likely of these alternative causes, and most expensive.
Regarding your scenarios:
1) CC solenoid is not a duty cycling solenoid, and to my knowledge it will not jump to limp mode when this solenoid is faulty. You will only get a code and troublesome boost above 4500rpm.
2) First/foremost route I would follow.
3) If the harnesses and solenoid check out, borrow another ECU for a quick test.
Onto code 51 / limp mode issue, which to my knowledge is entirely separate from a solenoid failure.
Have you replaced the fuel pump relays? (Maybe you can switch them with identical relays from a non-essential system just as a test, or borrow some known-good relays). If the relays are good, then if you have a multimeter and long test wires, you can manuall check the circuit when the ECU posts the code. Shake the wiring to see if it might be an intermittent short or open circuit. At this point using the wiring diagram (see the sticky thread at the top of this forum) to look for where this path appears at harness connectors and resume verifying each section of the path until you can isolate the bad harness. (Then if you confirm you have a bad harness, cry about the replacement cost).
Dave
05-23-06, 03:03 AM
#4
Junior Member
Thread Starter
Hi Dave, thanks for the info, just got a couple more questions/comments if you can help me out...
Ok, the only reason i was getting the idea they may be related is that they all seem to appear at the same time. I check the ECU every couple of days for a code, and dont get any, but when the car trips in limp mode, you will be sure to see 51 and 45 in the ECU.
51 goes away if i follow F64 of the workshop manual, but 45 hangs around. I thought 51 might be caused by the ECU not engaging the high speed relay while in limp mode (is this what limp mode actually is - cause it feels like it). I have also experienced 51 when i was dyno'ing my car, and hit the speed limiter (would this be the ECU cutting the high speed fuel pump relay?)
I dont know if the car is experiencing limp mode when i have this 45 code in my ECU (or im experiencing some other phenomenon) but it wont stop doing whatever it is doing UNTIL the second i get 45 out of the ECU - once that occurs, its all happy days...
Just as an aside, the problem i get is when the car comes out of vacuum and into boost. At 0 PSI the car begins to buck, stall, backfire and carry on if i try to push it. Driving under boost is just fine (the problems will not occur), free revving in neutral will not cause the problems (as im not boosting). Does this sound like limp mode, or am i getting myself confused here?
Thanks for the great description, I now understand its operation...
I see... I have tested it cold in car, but might have to pull off the UIM and get that sucker out... D'oh! Can't i just put my whole car in the oven so i dont have to take off the UIM 
The killer about this is, its a series 7, and these are a little rare in Aust (conversely i have people throwing series 6 computers around like candy). I dont imagine the computers/harnesses from these two series are the same, but ill check it out nonetheless...
I havent replaced the fuel pump relays just yet. I took the high speed relay out, bench-tested it and it seems fine (but like the solenoid, this was a cold test, so heat may be part of the equation?). Just checked the cost of those relays - 160 AUD each - ouch! Were you aware of any non-essential relays in the loom that are an equivalent for the fuel pump relay, so i can swap them as a test for the time being? I was looking around the engine bay, but the relays i have found in there dont have any elec specs on them (just random desmo part numbers on them, which when googled, turn up blank...). I guess they would all be of a similar nature wouldnt they (12V, x Amps)? Maybe remove one from an air-conditioner circuit or something like that?
I was lucky enough to end up doing this the last time i got the code. Wiring harness looks good all the way from the ECU plugs (continuity).
Originally Posted by dgeesaman
These issues appear to be entirely separate in nature - their only common elements are the main relay, wiring harnesses, and the ECU.
51 goes away if i follow F64 of the workshop manual, but 45 hangs around. I thought 51 might be caused by the ECU not engaging the high speed relay while in limp mode (is this what limp mode actually is - cause it feels like it). I have also experienced 51 when i was dyno'ing my car, and hit the speed limiter (would this be the ECU cutting the high speed fuel pump relay?)
I dont know if the car is experiencing limp mode when i have this 45 code in my ECU (or im experiencing some other phenomenon) but it wont stop doing whatever it is doing UNTIL the second i get 45 out of the ECU - once that occurs, its all happy days...
Just as an aside, the problem i get is when the car comes out of vacuum and into boost. At 0 PSI the car begins to buck, stall, backfire and carry on if i try to push it. Driving under boost is just fine (the problems will not occur), free revving in neutral will not cause the problems (as im not boosting). Does this sound like limp mode, or am i getting myself confused here?
Originally Posted by dgeesaman
Regarding your CC questions:...
Originally Posted by dgeesaman
heat causes the coil inside the solenoid to intermittently short or open, so the first thing to consider is testing the resistance of the solenoid both cold and hot (I use an oven at 90C to warm the solenoid for several minutes).
Originally Posted by dgeesaman
If the harnesses and solenoid check out, borrow another ECU for a quick test.
Originally Posted by dgeesaman
Have you replaced the fuel pump relays? (Maybe you can switch them with identical relays from a non-essential system just as a test, or borrow some known-good relays).
Originally Posted by dgeesaman
If the relays are good, then if you have a multimeter and long test wires, you can manuall check the circuit when the ECU posts the code.
05-23-06, 06:10 AM
#5
Well it sounds like all the basics have been covered well.
As for code 45 (CC Solenoid) causing the driveability problem - it may be that the series 7 ECU does respond differently to this error than the earlier versions. The fact that these both appear at the same time *might* suggest that if there is a harness short, that they are shorting between each other, or if they have a common ground that they might be damaged there.
When you get the code, definitely try testing the continuity of the solenoid at the harness connector - especially when the car is hot.
I wish I could give details about limp mode, but thankfully my car has never engaged it (yet). I have had major stalling and bucking once when I had bad fuel injectors, so it's not necessarily limp mode. A quick search should yield some details.
The relays are pretty basic to my knowledge. I don't know if they are interchangable, but with fuses in a pinch I've simply looked around for an identical fuse and swapped it out if I felt one was less important.
Good luck. Whatever you find, it's always nice if you can dig up this thread and post your results.
Dave
As for code 45 (CC Solenoid) causing the driveability problem - it may be that the series 7 ECU does respond differently to this error than the earlier versions. The fact that these both appear at the same time *might* suggest that if there is a harness short, that they are shorting between each other, or if they have a common ground that they might be damaged there.
When you get the code, definitely try testing the continuity of the solenoid at the harness connector - especially when the car is hot.
I wish I could give details about limp mode, but thankfully my car has never engaged it (yet). I have had major stalling and bucking once when I had bad fuel injectors, so it's not necessarily limp mode. A quick search should yield some details.
The relays are pretty basic to my knowledge. I don't know if they are interchangable, but with fuses in a pinch I've simply looked around for an identical fuse and swapped it out if I felt one was less important.
Good luck. Whatever you find, it's always nice if you can dig up this thread and post your results.
Dave
05-23-06, 09:02 AM
#6
RX-7 Bad Ass
iTrader: (55)
One thing I've thought about -
What year is your car? If it's a '96 or up, some of the ECU diagnostics may not apply, as they re-did the ECU in '96 and again in '99. That's a grey area.
The charge control solenoid should NOT put the ECU in any sort of limp mode. The fuel pump resistor relay very well could - that switches the fuel pump between 9v and 12v operation. If you were at full throttle with only 9v to the fuel pump, bye-bye engine, so I could see the ECU "limping" with that problem.
Considering it's an intermittent problem, it'll be tricky to find. Either a break in the wiring or a faulty solenoid that fails when heat soaked, as Dave pointed out.
Dale
What year is your car? If it's a '96 or up, some of the ECU diagnostics may not apply, as they re-did the ECU in '96 and again in '99. That's a grey area.
The charge control solenoid should NOT put the ECU in any sort of limp mode. The fuel pump resistor relay very well could - that switches the fuel pump between 9v and 12v operation. If you were at full throttle with only 9v to the fuel pump, bye-bye engine, so I could see the ECU "limping" with that problem.
Considering it's an intermittent problem, it'll be tricky to find. Either a break in the wiring or a faulty solenoid that fails when heat soaked, as Dave pointed out.
Dale
05-24-06, 07:49 PM
#7
Junior Member
Thread Starter
Apologies for letting this go by the wayside, just got back to check the thread then, and you both raise some good points Dave and Dale...
Dave, I seem to have located a harness joiner/connector containing the charge control solenoid in the engine bay (near my diagnostic port) so ill be sure to do some tests along the lines of what your are suggesting the next time i see the car acting up in a hot state.
If i find some results I will definately try to post some info in the hope that it might help others!
Dale, the ECU being different (and generating different error codes) is something i have considered, but dont quite know how to handle... (its hard enough to find someone with a diagnosis tool for a series 6, let alone a 7 - ive just resigned to flipping the codes out myself with a LED in the hope that they are the same - but your dead right - I could well be being led on a wild goose chase
I'm going to try my luck on the net with finding error codes for the 7, and if i get luckly ill try and flick something up on the thread...
I'll keep an eye on the prob and see what I can dig up, in the mean-time, thanks for giving some info my way guys... much appreciated...
Dave, I seem to have located a harness joiner/connector containing the charge control solenoid in the engine bay (near my diagnostic port) so ill be sure to do some tests along the lines of what your are suggesting the next time i see the car acting up in a hot state.
If i find some results I will definately try to post some info in the hope that it might help others!
Dale, the ECU being different (and generating different error codes) is something i have considered, but dont quite know how to handle... (its hard enough to find someone with a diagnosis tool for a series 6, let alone a 7 - ive just resigned to flipping the codes out myself with a LED in the hope that they are the same - but your dead right - I could well be being led on a wild goose chase
I'm going to try my luck on the net with finding error codes for the 7, and if i get luckly ill try and flick something up on the thread...
I'll keep an eye on the prob and see what I can dig up, in the mean-time, thanks for giving some info my way guys... much appreciated...
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06-29-06, 04:05 AM
#8
Junior Member
Thread Starter
Ok guys, little update on what has happened....
I took the car in to the workshop to get the Solenoids replaced, and it seems to have fixed the prob. No more limp mode characteristics, car boosts well, driver is happy!
Thanks for your help on this one;
Sco.
I took the car in to the workshop to get the Solenoids replaced, and it seems to have fixed the prob. No more limp mode characteristics, car boosts well, driver is happy!
Thanks for your help on this one;
Sco.
