I've swapped out the boost sensor in my S4 turbo twice and im still not getting a reading on my Rtek. Its also throwing a code for it.

Any ideas?

 

Yeah. Put a meter on pin 2B of the middle plug of the ECU and with the key ON engine OFF see if you read 2.3 to 2.7 vdc or not. You leave ALL plugs connected and backprobe the brown/red wire in 2B to do that.

And or you can put key ON engien OFF and go to the boost sensor. Unbolt it from its bracket. Turn it up so you can backprobe the brown/red wire. Same results should be there as what I wrote above.

No output? Then see if the black/white wire in that plug has batt voltage. See if the brown/white wire has approx 5vdc.......ohm out the pure black wire and see if it reads less than 0.5 ohms..........

IF you have 2.5 to 2.7 AT the boost sensors brown/red wire with key ON and nothing at the brown/red at the ECU...............the wires open b/t the sensor and the ECU plug.

Ought to take fifteen minutes for you to check out the boost sensors plug. Remember all plugs are left connected and the engine OFF, key ON.

 

I have 10.8 volts. Key on, not running.

 

10.8 at brown red

10.5 at black white

Brown/white has 4.9

I don't have a solid black. I have a brown/black.

This may be an N/A harness if it matters. The PO did a hack swap.

 

Read post #7 by HAILERS and see if this is similar to your problem. You could remove the Meter fuse and w/key to on take the voltage once again on the Brown/Red wire again and see what voltage you get.

https://www.rx7club.com/showthread.p...hlight=tps+rod

 

That's exactly what's going satch. Im getting very close to battery voltage at 2b. Also my harness has shitty spade connectors for the alternator hook up telling me this wasn't done right.

I've been chasing electrical problems with this car from day one and I have most of them figured out.

Now I need to know what has to be done to allow my ecu to read my boost sensor.

N318 ecu and n318 boost sensor

 

The boost sensor can't output more than 5vdc max on a series four non turb or turbo car.

Your seeing ten something so there must be something spliced into the brown/red before it gets to the ECU. On a turbo car there is a wire spliced in that brown/red. This spliced wire goes to the instrument cluster to feed the boost gauge.

So I'd remove the plugs from the instrument panel and then go retest the input to the ECU on the brown/red wire.

First you might try what Satch said and pull the meter fuse in the interior to see if the brown/red now reads less than five volts. Maybe it is that fuse feeding power to the brown/red in some fashion.

I'm going to assume you did as mentioned when testing the wires. Leave all plugs connected to the items and backprobe the connectors/wires when looking for voltgae.

Black/White on the sensor is switch volage and should read batt voltage. I'm assuming your battery is low when you did this test.

OR if you know how to remove a wire from a connector, like at the boost sensor, you could remove the brown/red wire and then turn the key ON. Check the terminal in the sensor for voltage and see if it now reads around 2.7 vdc or not. That would prove that there is another wire spliced into the brown/red causing the problem .

Or pull the plug off the boost sensor and check for voltage on the brown/red wire with key ON. Write back what you see. I frankly forget what it would read like that but I could compare it with one of my cars..perhaps.
Worst case scenario...................real worse case..............cut the brown/red at the sensor about four inches back from the plug. Splice the four inches to a new wire. Route new wire to the ECU's middle plug where the 2B is. Cut the brown/red four or more inches back from the middle plug on the ECU. Splice the other end of your new wire to the four inch section left in he plug. Done. Cap off the end of the rest of the brown/red wire at the ECu and at the sensor.

I'd jump thru a few hoops before cutting that brown/red wire. You'd lose your factory boost gauge reading doing the cut and splice thing.

 

Looking further.................it seems to be a mismatch of harnesses somewhere.

See the stk wiring for a turbo car. See the boost sensor and the BrR wire and how it goes to the ECU but also splices off and goes to the boost gauge.

Take particular note of the FEM-01 in that picture. That is an electrical plug. It's called that because that plug mates the FRONT harness with the EM harness on the engine. Therefore FEM.

Now remember this. On a non turbo car the BrR wire goes directly from the sensor to the ECU's pin 2B.

So I looked at how a Turbo cars FEM-01 is wires with how a NON turbo cars FEM-01 is wired.

Hmmm. I'm still figuring how this works exactly. I'll post later.

This is a TURBO car. Right? I need to know. OR is it a non turbo swapped to turbo. I'm too lazy to go reread everything. I'm busy right now.

 

meter fuse pulled, boost sensor unplugged, key on, not running im getting battery power at brown/red on the boost sensor clip.

I have an n/a cluster so losing what would be the boost gauge is not an issue.

I have no problem running new wires but seeing that im still getting 12v at brown/red would that solve anything?

Does the sensor send voltage to the Ecu? Or does the Ecu send voltage to the sensor?

I really appreciate the help guys. **** is getting aggravating.

 

Its an n/a shell with turbo swap.

 

Well now that I think about it, if the engine had a non turbo EM harness on it that would not effect the path from the boost sensor to the ECU and the FEM-01 would not be a player.

If he had a TURBO EM harness on the car, but was using a non turbo FRONT harness then I can see how FEM-01 would ball things up. Front harness being the one that runs from the right side interior to the left interior..........out into the engine bay on the left side of the engine and on to the front of the car.

I'm starting to think installing a new wire to replace the brown/red one might be the easy answer. There's a couple of unknowns here as to what harness is which as far as Turbo vs non turbo.

I think for right now the COOL thing would be to depin the brown/red at the sensor and then reinstall the plug on the sensor. Then key ON and see what the voltage is on the pin where the brown/red WAS in the sensors jack. Should be 2-5 vdc or pref 2.7vdc. Which proves the wiring in the EM harness is .....corrupt/wrong.

 

The sensor sends voltage to the ECU.

 

THAT solves the problem.

Find FEM-01. Pull the plug apart. The half of the plug that is the EM half needs to have the BROWN/RED wire extracted from it OR cut four inches back and deadend the Brown/Red wire.

Your backfeeding batt voltage from the FRONT harness side of FEM-01 to the boost sensor AND the ECU. Not allowed for things to work right.

Plugs FEM-01 and FEM-02 are colored ORANGE and are located in the passengers foot well on the right side of the passengers compartment.

The FEM-01 has 15 wires in it so you can distinguish it from FEM-02 which has ??? 13 wires in it.

For this to be right the harness on the engine would have to be a TURBO EM harness and the rest of the car harness is non turbo.

 

.

 

Im pretty sure all the harnesses in the car are N/A.

Can I just run a new wire from brown/red at the ecu to the brown/red at the sensor? This would be easier. Or will that not work?

I have no idea what is turbo and what is n/a. Half of the clips in the engine bay were missing.

 

I just cut brown/red at the ecu and at the sensor. That piece of wire still has 12v so it was definitely backfeeding. From brown/red on the sensor I now have 2.5v. Im gonna run a new wire.

 

I'd guess the harness on the engine is probably turbo EM harness.

The turbo EM harness does not have the small plug for the alternator, but the non turbo car does have the alt wires. On a turbo car the alternator wires are on the harness on the left side of the engine bay. Same harness that carrys the CAS wires.

 

I wish I knew more about the harness, but I don't. I ran the new wire and the sensor reads perfectly.

However, the car seems to be breaking up a bit when I rev it. Would that wire that I eliminateed power something else?

Thanks again for the help.

 

Do you get the same reading at the ECU as the sensor itself?

 

Yea same reading.

I think it was breaking up because my thermosensor clip was off. Im charging my palm now.

 

There is a B/W wire in the front harness part of FEM-01 and it was feeding batt voltage to your Turbo EM part of the FEM-01 and if you had a normal non turbo car that black/White would have fed power to the small plug on the alternator.

It right now feeds nothing and it was not feeding anything before you cut the brown/red other than the boost sensor.

There is another wire in that FEM-01 that went to the alt small plug on the NON TURBO car but now is going to ground and it should not. I often wonder why that isn't noticed in these swaps that are not quite right.

It seems the Warning Lights should all come on and stay on with it wired like this. Have you noticed anything funny about how your warning lights worK? I used to say you'd blow the METER FUSE having it wired like this, but I finally realized that that wire comes off the coil of the alt relay in the CPU and the worst that can happen is the warning lights all come on and stay on as long as the METER fuse is good.

 

My warning cluster is replaced with gauges so no lights are on. Im not getting a buzzer either.

The car was running good when I left it. Went to a mothers day buffet today which made me nap and lose all motivation. Ill be back at the garage sometime this week.

Hailers and satch, you guys need a "donate" link.

 

yeah no ****. they should combine forces and have a script on a website and have the 20 questions game but instead of trying to figure out the object, it tried to figure ou the culprit to the problem. blamo.