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Quite usefully... I cannot see forum pictures right now for some reason. Any how.. I don't really have a helper to hand that I can use.. Maybe at the weekend.. I would like to wait and do the light check when I can get my cluster back first I think. manually operating the motor and solenoids together feels a little dodgy? not sure why.. But it gives me a slightly uneasy feeling if I am honest! So until I get my cluster back I am stuffed. Stick with me and I will update as soon as I can.
Just been having a thought the last couple of days and checked it out on a wiring diagram. In the absence or a cluster would I be correct in thinking I can still test the ABS light Function by wiring a bulb between the G/O C1-01 pin and B/Y pin? the latter should be ignition live and the former is the ground circuit from the ABS ECU you spoke of before?
Am I right??
I understand your trepidation about wiring up the ABS Pump. It was an attempt to brainstorm another idea. It may also not be a wise idea to have extra wires criss-crossing over one another. In certain circles, technicians refer to that ball of wires as a "spaghetti lab".
You may simulate the ABS Bulb from the instrument cluster. I like your method of thinking! You could use any 12V bulb (any wattage under 2W is ok) or even use your test probe. However, the correct pins would be necessary. The pins you cited are electrically the same. The proper electrical connections are to connect the Positive lead of the test probe (or bulb) to Connector C1-01 Pin 2D. That is the +12V switched source from the METER fuse. Then, connect the Negative lead of the test probe (or bulb) to Connector C1-01 Pin 1B, which is the Ground (earth) input to the ABS Bulb from the ABS CPU & Hyd Unit.
NOTE: When testing the ABS Light Bulb with the Hyd Unit and ABS CPU connected you must ensure the engine is running. Otherwise, the ABS Bulb will never extinguish. After the car is started, the bulb should extinguish after 2-3sec as part of a lamp test diagnostic.
Without the need to find the old post, here are the test procedures:
1. Connect all ABS system Connectors.
2. Start the car and let the engine warm up (we don't want any potential flood situations). After 2-3sec, does the ABS light illuminate?
---We anticipate a "YES" response.
---This is a good time to test the Alternator, see my remark below.
3. Shut off the car (engine not running). Disconnect Connector O-01 from the ABS CPU.
4. Start the car and let the engine run for 5min. After 2-3sec, does the ABS light illuminate?
5. Shut off the car (engine not running). Reconnect Connector O-01 to the ABS CPU then disconnect Connector O-02 from the Hyd Unit.
6. Start the car and let the engine run for 5min. After 2-3sec, does the ABS light extinguish with Connector O-02 disconnected?
7. Disconnect all test equipment then reconnect and verify any/all connectors.
Do you still have a 2nd ABS CPU? As I read some of your older posts, you tested a 2nd unit. Unless I misunderstood your comment about it, you turned the key to Position 2. Does that mean you did not start the car? If you still get the same result from the test above (ABS Light constantly on) then swap out the 2nd ABS CPU and repeat. Again, I cannot stress enough the need to have the engine run for this test procedure because there is a connection to the ABS CPU and Alternator.
Speaking of Alternators, how is yours? Have you tested it for proper operation? While the engine is warming up in Step 2, follow the Charging System Troubleshooting matrix on Pg G-8 in the FSM. Specifically, Step 4. As another option, you could remove the alternator and bring it to an auto parts store for output and load tests. Do they offer that kind of service in UK parts stores?
Could you also take a hi-res photo of the ABS CPU and the Hyd Unit Connectors?
Thanks for posting those steps again George. I have a bulb and wire ready for a make shift light worst case scenario. I won't get around to firing up the car until over the weekend though now. Had a loan offer for a couple of sets of clocks too but it just comes down to getting them before the weekend which is unlikely.
Will keep you posted as soon as I have news! Will be a bonus to put the abs computer and rears trims back once I know what is what!
I got my cluster back at last.. not fixed by the look of it and worse than before in fact! Another story. So I have just been out and run the car up to follow the final test procedure. Results were as follows.
plug O-02 disconnected. Light remains illuminated after engine start.
plug O-02 connected and plug O-01 disconnected. Light remains illuminated after engine start.
all plug screen connected light remains illuminated.
So lastly I swapped out the spare ABS computer and and soon as the engine cranked I noticed the light flickering.. and yes you have guess when the engine started the light went out!? WTF?!
Now.. I am not 100% convinced this is the issue solved yet and am half expecting the light to come back on the minute I go for a drive. Which I cannot do just yet. Hopefully can we see soon.
Question is whether the rest of the light illuminations are as expected. I imagine it would go off when O-01 was unplugged?
thanks for all the info so far.
One big big point to take home from this thread is the engine MUST be running to fully test the ABS light response!
It is good to hear that you made progress. It's a good thing that you still have the spare ABS CPU too. I do have questions after you installed the 2nd ABS CPU:
1. What do you mean by light flickering when the engine cranked over?
2. Was the ABS light illuminated along with the other lights when you turned the ignition to ON (Engine not running)?
3. Did the ABS light shut off along with the other lights when you turned the ignition to START (Engine cranking)?
4. Did the ABS light illuminate then shut off after 2-3sec once the engine started?
5. Did you repeat the same test procedures (from Post #78) with the spare ABS CPU?
6. Did you verify the alternator produces proper voltage at terminals B, L, and S, according to Charging System Troubleshooting Step 4 (Pg G-8)?
I agree that we are not out of the woods just yet. I still believe the diode in your Hyd Unit is a problem but it may play a minor roll. A test drive would certainly shed more light (no pun intended) on the problem. What prevents you from a low-speed test drive, say 5-10mph down a small segment of street, parking lot, or driveway? We would only need to verify the ABS Light doesn't illuminate when the car is in motion.
We had many discussions that addressed resistance checks of the ABS system and even applied voltage to test each Solenoid & Valve on the Hyd Unit. Could it be possible that this statement form Post #27 didn't register when addressing the engine running revelation?
"...In order to properly test the ABS warning light, the engine must be running. Otherwise, when the key is set to ON, the ABS light will always stay on. I observed this indication in my FD today."
Perhaps Dale's extra chime-in helped to sew the seed? Nonetheless, we are much closer to solving your problem!
As a separate note, what is happening with your instrument cluster? Would you care to share that problem in a separate thread?
Hi George, the comment in post #27 did register but at that point we had done a number of checks already and most people I speak to seem to be of the opinion the ABS ECU is an unlikely candidate. . But this is why I wanted to get my cluster back and check the light with engine running at this point.
With the second ECU the light was on with ignition on, when cranking it was illuminated too but appeared to flicker dim-bright slightly which I had not noticed before but may not have been paying attention.. I did not time the light going out when the engine started to run but I would say pretty instant. At most a couple of seconds. I did not follow and further test procedures with The spare ECU as the light went out and I had already stop started a number of times and did not want to push my luck! I have a voltage readout on my ecu and that displays just over 14 volts when engine is running so I assume I am all good there unless I am missing a point ? Main thing I want to know at this point is if I can put my ABS computer back in place and refit my boot trim?
i cannot drive the car as half the front end is off waiting for a wing to come back from paint! Should have been last weekend. Now Monday!
Cluster wise That is a whole long story.. maybe I will send you an email over later.
Thank you for responding and answering my questions. Your observation of the ABS light flicker is normal. When cranking the engine, the warning lights should shut off because the battery cannot supply enough current to the starter and all the other electrical bits. They may appear to blink or dim dependent upon the time it takes for the motor to turn over.
When testing the alternator, it is best to measure the voltages according to the test procedures. I am not discounting the measurement from your ECU display. Testing the voltage at the source removes any doubt to the output of the alternator. Additionally, there are specific voltage ranges measured at each pin when the engine is running and when the engine is shut off. For example, I use an Apexi Turbo Timer. I use it more as a voltmeter than anything else. When my engine runs, the display on the TT typically reads 13.4 - 13.6V. This weekend, I measured the voltage output of my alternator at Terminal B and it measured 14.1V. This error comes in the way of transmission line loss, electrical loads, and how the TT measures the voltage. The point I wish to make is that a car's gauge is an indicator. When a component's accuracy is required then testing it with equipment independent from the car eliminates any error.
I know that you are anxious to reassemble the car's boot. I would ask that you hold off. I presume that your spare ABS CPU is now installed in the car? Would you be willing to test ABS Light according to Post #78 with the new ABS CPU? I am very curious to see how the system reacts when the Hyd Unit is disconnected. Otherwise, feel free to button up the boot! Since you identified that the original ABS CPU is suspect, would you also be willing to open its case and inspect/photograph its circuitry?
Hi George, happy to pull the plugs again when I next run the car.. maybe at the weekend to try and re-calibrate my rev counter! So to avoid excessive stops start as I will no doubt need a few are you just interested to see what result I get when the pump connector is unplugged? I will check out the test procedure for alternator and do this at the same time. I would have anticipated that if the alternator output was causing the ABS light then the light would have stayed on with the new ecu as it does not require the car to be moving to detect it? Still happy to check the outputs and rule it out.
Would be great to take it for a drive.. slim chance I will have my wing.. (fender) back in the week and be able to get the car together ready for a short drive.. assuming we get some dry weather at last!
I will look at pulling the abs ecu apart once am sure if that is the fault or not. Don't want to pull something apart if it is in fact good and saleable!
I would like to say a big thank you to George for step by stepping me through a logical fault finding process... as it happens it appears my first port of call was the answer to the fix. I still have a niggle in my mind something could come back and bite me but we will see. So far after changing the abs computer and all importantly starting the engine the light has gone off and stayed off even after a couple of drives around the block! A little thumbs up at least!
So lesson to learn.. be sure to start the engine to check if the abs light goes out!
Thank you for those kind words. It is good to hear that the ABS problem was resolved. Now, if you really want to be adventurous, open up the bad ABS CPU and let's look for anything broken, burned up, or corroded! Maybe that project could wait until your instrument cluster is in good nick (good condition, for us Americans)?
The bigger question to ask: are you confident enough in the ABS repair to celebrate with a drink?
Cheers,
George
P.S. I don't know why I should care about this but...when time permits, feel free to hit the "Thank" button on any post that helped.
I say, drink now to celebrate fixing the ABS then drink again to celebrate passing your MOT!
The Thank button can be found at the bottom right corner of a post. It would only be available on another member's post. For example, you should see that button in Post #87.
This sample photo is what I see on your post:
Thanks Button in lower right corner of another member's post.
Rehashing an old thread since I seem to be experiencing similar problems without define answers from what I've found so far, so looking for some suggestions.
Mines a 93 R1, so blue label ABS module. Symptoms were consistent ABS light on start up. I seem to have remedied that by fixing some corroded pins in the rear connector on passenger side, I don't recall the exact connector. Now have ABS light only when moving. Steps I've been through have followed the FSM for testing and all wiring seems to be good from the front of the car to the rear ABS computer. I thought I had the ABS light narrowed down to to the front left sensor as it would only come on when spinning that wheel with the car in the air. Light does not come on when spinning other wheels currently. So I replaced the front left sensor with a new factory Mazda one from Amemiya, they use a different part number (F146-43-73X) but are available. Spin the wheel front left wheel after replacing the sensor with the car up in the air and throws the ABS light on again. So I'm thinking ABS control module in the rear, replace it with a used blue label one, and same problem. I've gone back to testing up at the pump and FSM show testing pins in the main connector to the pump. Testing the diode is continuity from green/yellow to green/orange wire, and I seem to not have any continuity between those wires. What's throwing me off is why is my ABS light only coming on when only the front left wheel spins but does not come on from when any other wheel spins?
I've tested resistance on the new ABS sensor and it's above what the FSM states (1.700 Ohm) and FSM says between .8 -1.2. So I hook up the old ABS sensor since it tested in spec and I still get the ABS light. If it is an fact a diode problem can they be replaced? If so can someone point me to a thread that show a part number or how to? So any suggestions on where to go from here are appreciated.
How does the tone ring look on the front left wheel hub? Is the tone ring loose or have missing/damaged teeth? Double check the alignment of the Wheel Speed Sensor to the wheel hub and tone ring. Compare the spacing of the front left sensor to the front right sensor (wheel speed sensors). Do you see anything unusual?
Could you also repeat the test on Page P-52 of the FSM, Steps 1 through 3. Make sure you have AC Volts selected on your multimeter when checking for Wheel Speed Sensor voltage according to the table. You should read 50 - 60 mV AC (millivolts, Alternating Current) at the ABS Control Unit Connector, O-01, Pins 1K to 1G, 1U to 1F, 1O to 1Q, and 1L to 1P.
Most importantly, please identify the connector that you had to repair. Corrosion may have crept up the wire insulation and may be causing other issues. Could you explain the repair you performed on this connector?
Did you check for an open circuit on the ABS Control Unit connector, O-01 Pins 1D, 1S, and AF? Check each pin for continuity to chassis ground. They will be black wires. If there is a problem here then a repair to the ground wires will be necessary.
Did you also test your alternator output? If it's out of spec then it will affect the ABS circuit.
Ok, did some more testing tonight. Tone ring and sensor spacing all look good. Speed sensor voltage is within specs, no open circuits on 1D 1S or AF. Did not go through alternator test procedure this evening but 99% sure it's good when I was troubleshooting a previous issue early this summer. Checked front and rear valves for continuity at 0-02 connector hydrolic side, all check out good. Checked motor relay, good. Checked 0-03 connector for battery voltage, it's correct. Also checked 0-03 for continuity on R/Y wire hydraulic unit side, good. Have not checked brake light switch, is very difficult to get to with test leads but did notice green wire must have gotten hot at some point as connector is slightly melted around spade terminal and that same wire insulation is slightly charred. So maybe some resistance there and will need to dig into this further, but brake lights are functional. One other thing that kinda stands out. On the diode test astested above on post#85 I get 600 Ohms in my test. Post #85 states I should have 660 Ohms. Not sure if that's enough difference to mean anything so any input on these 2 items are appreciated.
Also thanks again to Gen2n3 for diving back into this to help figure it out
Mike H
I seem to recall the diode measurement of 660 ohms was displayed on my DMM. As long as it reads 600 ohms in the direction I specified and infinite ohms in the opposite direction, then the diode is good.
On separate good news, it looks like all 4 Wheel Speed Sensors are good. So we just eliminated that problem. Additionally, you verified grounds are good too.
I would venture to say that charred wire to your brake light switch should be investigated further. Please refer to the Wiring Diagram Manual (WDM), Diagram F-3 (Pg Z-64) to trace the stop light switch wires. Additionally, verify a 20A fuse is installed in the STOP fuse box slot. The Stoplight Switch wire is Green going to the tail lights, high mount stop light, ABS Control Unit, Cruise Control, ECU, and for those with Auto Trans: A/T ECU & Shift-lock control unit. The wire is Green with White stripe going from the switch to the fuse box, marked 20A STOP.
P.S. You may want to print out the schematic diagrams and use color pencils to mark the wires you tested and their status. This will help you track your progress and may help identify the problem.
Last edited by Gen2n3; 10-04-22 at 10:26 PM.
Reason: Added post script.
Measure the resistance (not just continuity) between Connector O-01 Pin 1N (Green wire) to Connector F3-01 bottom pin (Green wire).
Do you know how to use the car chassis as a conduit between these 2 wires? This will prevent you from stringing wires from one end of the car to another.
If not, then follow these easy steps:
1. Connect DMM Red (positive) lead to O-01 Pin 1N (Green wire).
2. Connect DMM Black (negative) lead to chassis ground (make sure it's bare metal, no painted surface).
3. Disconnect Connector F3-01 from brake switch.
4. Connect a jumper wire from F3-01 bottom pin (Green wire) to chassis ground (again, bare metal contact).
5. Set DMM to highest resistance reading (if it doesn't have an Auto range function).
6. Turn DMM on then read measurement.
7. You may have to reduce the scale of the DMM to a lower setting to get a more accurate measurement.
Well back at it and was able to track down a factory Mazda ABS tester. Hooked up per the directions and started running test. Got a fault on the motor relay. I just happen to have a new one since I've been having this problem for a while just never installed it. Put in the new motor relay, spin front left wheel and throws the ABS light again. Ran the rest of the test and sensors on all wheels are good, Solenoid test came back good, so not sure where to go from this point. Any suggestions?
Update. Did some tests with the Mazda tester and it appears the pump motor is not working. I do not get the pump to run for the test. So that would explain why switching to the new relay didn't work. I'm assuming I need to find a new ABS unit or is this something that can be repaired or fixed in a rebuild?
Bring this back up again. Did some more investigation at the X10 connector for the front left wheel speed sensor to make sure there was no corrosion on any pins. All looks good in that connector but now ABS light is on constantly from start up. Previously was only illuminated when spinning front left wheel. Also, now noticed ABS control module in the rear is flashing red light. I get 10 long blinks then it starts over. Digging through the FSM in section P does not show what the codes should mean, nor could I find info via Google so I'm at a loss on this.
Any help is appreciated to help determine what the 10 blinks mean.
I'm having this issue as well Mike93r1. My 94 has had this light on since purchase. A road test showed the front passenger wheel locks up. The speed sensor on that side tests good, same resistance (ohm) as the driver's front. All fuses are good.
What does your abs tester look like? Can you send a pic? I found one for sale locally but the seller cannot confirm that it works.
04-10-18, 06:49 AM
