Questions on wiring on OBD2 S52 engine bay

[wodcutr]

Update - Found the problem! Probed the abs connector pins 2 and 23 to see if the signal from the RR sensor was getting to the computer and there was nothing there. Hooked up a spare sensor and still nothing.

Decided to check wires for continuity and both had no continuity from sensor plug to connector. Started tracing back the wires from the plug toward the computer and found that some fool (PO) had cut both rear sensor wires. PO was a car audio "expert" and had removed all the stereo wiring in the whole car when the interior was stripped out planning on running his own system stuff. Wires look similar to the stock speaker wires so he probably cut them thinking they were stereo speaker wires. Grrrrrr!

Spliced the wires back together and ABS and CEL went out in the dash. That problem solved I can now remove the ASC bulb in the cluster and enjoy driving my new drift monster 332ti!

Thanks everyone for all the help getting this car sorted. If anyone else has questions regarding this swap feel free to contact me and I will be glad to help out.

Dan

[Deeznutz]

Originally Posted by wodcutr

Update - Found the problem! Probed the abs connector pins 2 and 23 to see if the signal from the RR sensor was getting to the computer and there was nothing there. Hooked up a spare sensor and still nothing.

Decided to check wires for continuity and both had no continuity from sensor plug to connector. Started tracing back the wires from the plug toward the computer and found that some fool (PO) had cut both rear sensor wires. PO was a car audio "expert" and had removed all the stereo wiring in the whole car when the interior was stripped out planning on running his own system stuff. Wires look similar to the stock speaker wires so he probably cut them thinking they were stereo speaker wires. Grrrrrr!

Spliced the wires back together and ABS and CEL went out in the dash. That problem solved I can now remove the ASC bulb in the cluster and enjoy driving my new drift monster 332ti!

Thanks everyone for all the help getting this car sorted. If anyone else has questions regarding this swap feel free to contact me and I will be glad to help out.

Dan

So i just finished my swap that i started last year my build thread here http://www.318ti.org/forum/showthread.php?t=41996 i too have no working abs and can't figure out why because it worked before the swap when it had m44 in car. Now i have no abs so can you please clarify where in car you traced those signal wires to/from also i have aftermarket tune so no CEL for emissions equip, but i really want my abs to work.
also are you certain abs is functioning have you road tested it? My ABS light come on few seconds after engine is running
my car is 97ti with s50b30 using 97m52 auto harness and 97m52 ecu.

[Trusted-1]

Originally Posted by Deeznutz

So i just finished my swap that i started last year my build thread here http://www.318ti.org/forum/showthread.php?t=41996 i too have no working abs and can't figure out why because it worked before the swap when it had m44 in car. Now i have no abs so can you please clarify where in car you traced those signal wires to/from also i have aftermarket tune so no CEL for emissions equip, but i really want my abs to work.
also are you certain abs is functioning have you road tested it? My ABS light come on few seconds after engine is running
my car is 97ti with s50b30 using 97m52 auto harness and 97m52 ecu.

It is unlikely your problem is the same as Dan's since his car had wires cut by the previous owner.

The ABS light will be on if the stepper motor is not connected to the old M44 Throttlebody ASC unit. I read a post somewhere that said you could use a resistor in place of connecting the motor but the ABS light will be on if that is not connected.

That's the first thing I would check anyway. Good luck

[wodcutr]

The ASC and the ABS are run by the same computer which is located under the glove box, closest to the speaker panel. They both use the speed sensors on each wheel to detect slippage from acceleration or braking. The ASC tests itself on each startup by actuating the cable that is supposed to be attached to the secondary throttle body to see if that TPS gives signal that it is moving. If the actuator motor / resistance is not plugged in as well, it will trigger both the ASC and the ABS lights.

The ABS system also checks to see if all sensors are there and with the proper resistance, as well as pump solenoid readiness too. If ABS light is on at startup then you have a bad sensor, fuse, or possibly pump. If the light goes out after startup but comes on when moving then you have a bad sensor.

If I were you I would test all sensors to see if they are good. If all test good then you need to verify that the wiring is good to the computer by testing each set of pins in the harness for the same resistance the sensors are showing. You will need a wiring diagram to know which pins to test for each sensor. If all that tests well, then you either have a bad pump, relay, or computer. You have to systematically eliminate each potential source of a problem to get to the bad part. Electrical issues can be a huge pita and time consuming, but they are all traceable. Start with the easiest stuff first like fuses and sensors and know not guess they are good.

Also just wanted to verify that you shimmed the rear sensors if you used e30 axels, otherwise both rear sensors are junk due to rubbing against the ring.

[Deeznutz]

Originally Posted by wodcutr

The ASC and the ABS are run by the same computer which is located under the glove box, closest to the speaker panel. They both use the speed sensors on each wheel to detect slippage from acceleration or braking. The ASC tests itself on each startup by actuating the cable that is supposed to be attached to the secondary throttle body to see if that TPS gives signal that it is moving. If the actuator motor / resistance is not plugged in as well, it will trigger both the ASC and the ABS lights.

The ABS system also checks to see if all sensors are there and with the proper resistance, as well as pump solenoid readiness too. If ABS light is on at startup then you have a bad sensor, fuse, or possibly pump. If the light goes out after startup but comes on when moving then you have a bad sensor.

If I were you I would test all sensors to see if they are good. If all test good then you need to verify that the wiring is good to the computer by testing each set of pins in the harness for the same resistance the sensors are showing. You will need a wiring diagram to know which pins to test for each sensor. If all that tests well, then you either have a bad pump, relay, or computer. You have to systematically eliminate each potential source of a problem to get to the bad part. Electrical issues can be a huge pita and time consuming, but they are all traceable. Start with the easiest stuff first like fuses and sensors and know not guess they are good.

Also just wanted to verify that you shimmed the rear sensors if you used e30 axels, otherwise both rear sensors are junk due to rubbing against the ring.

A couple of things to note
Yes I shimmed rear sensors for e30 axels will test them again but as I said b4 abs was working b4 swap

Yes ASC and abs light come on but as stated b4 abs light comes on after engine is running not when first started...eg. I'll turn key to start car and all light are on when actually starting only ASC light stays on abs goes out, then after about 5-10 seconds abs light comes on.

I don't care about ASC I can remove bulb but I do want abs, I too was also thinking about CAN bus high/low signal that it's not getting. I will test sensors again but I doubt the problem is bad or failed electrical I think and wanted to know what signals/wires if any I needed to move, cross or change in order to get abs back?

[Deeznutz]

Originally Posted by Trusted-1

It is unlikely your problem is the same as Dan's since his car had wires cut by the previous owner.



The ABS light will be on if the stepper motor is not connected to the old M44 Throttlebody ASC unit. I read a post somewhere that said you could use a resistor in place of connecting the motor but the ABS light will be on if that is not connected.



That's the first thing I would check anyway. Good luck

Do you know what type of resistor I can use for this? I don't want to plug in old unit nor do I know if I still have it

[Deeznutz]

Good news to report I found an old ASC stepper unit at my friends and plugged it in ABS is off for good now ASC light stayed on. So Trusted-1 was absolutely right thanks! Only thing now is what type of resistor to plug in its place I don't want that clunky looking thing in my engine bay

[Trusted-1]

Post on Bimmerforums about ASC delete says 10ohm resistor does it on 6 cyl car.

http://www.bimmerforums.com/forum/sh...54#post9444754

Using ohms law, 12V at 10 ohms is 1.2 amps and 14.4Watts of heat to dissipate (but the post says only a 1 watt resistor is needed?)

Maybe the ASC motor gets a lot less than 12V but if it were me, I'd start with a 400ohm resister and work down from there and see what the highest value that tricks the ABS/ASC circuit into thinking it's connected.

You could also measure the resistance of the motor, match that and use an online ohms law calculator to see what wattage resistor was needed.

Steve

[Deeznutz]

Originally Posted by Trusted-1

Post on Bimmerforums about ASC delete says 10ohm resistor does it on 6 cyl car.

http://www.bimmerforums.com/forum/sh...54#post9444754

Using ohms law, 12V at 10 ohms is 1.2 amps and 14.4Watts of heat to dissipate (but the post says only a 1 watt resistor is needed?)

Maybe the ASC motor gets a lot less than 12V but if it were me, I'd start with a 400ohm resister and work down from there and see what the highest value that tricks the ABS/ASC circuit into thinking it's connected.

You could also measure the resistance of the motor, match that and use an online ohms law calculator to see what wattage resistor was needed.

Steve

Thanks for the feedback I'll test the stepper with my multimeter and report back

[Deeznutz]

Resistance came out to 4.5 ohms

[Trusted-1]

It is likely a higher value will still trick the controller into thinking it is attached especially since the other guy tested a 10 ohm.

I'd go for a 15 watt resister based on the Ohms law calculator.

Although it would only get powered in a wheel slip scenario, the resister has to dissipate the heat (wattage) of the voltage when it is active.

If you were at an autocross or similar event and did not turn "off" ASC, it would seem like the one watt resistor could fry.

[Deeznutz]

Originally Posted by Trusted-1

It is likely a higher value will still trick the controller into thinking it is attached especially since the other guy tested a 10 ohm.



I'd go for a 15 watt resister based on the Ohms law calculator.



Although it would only get powered in a wheel slip scenario, the resister has to dissipate the heat (wattage) of the voltage when it is active.



If you were at an autocross or similar event and did not turn "off" ASC, it would seem like the one watt resistor could fry.

Do you think the computer would try and activate the stepper motor since ASC light is on and ASC/abs module don't see hi/low bus signal?... I did auto X this past weekend and know for sure my abs works felt it kick in

[Trusted-1]

You may be correct that the ABS is actually working even though the light is on.

Not sure why the ABS light is tied to the ASC motor...

I get that they both use the wheel sensors but it seems like the missing motor should only activate the ASC light.

[M3 s52 guy]

So I recently swapped my engine harness on my s52 m3 an I’m getting a temperature code po116 an no start . I’m novice when it comes to wires if anyone could maybe think of which two wires I could’ve have mixed up maybe a common mistake of one ? Anything can help

[Trusted-1]

Originally Posted by M3 s52 guy

So I recently swapped my engine harness on my s52 m3 an I’m getting a temperature code po116 an no start . I’m novice when it comes to wires if anyone could maybe think of which two wires I could’ve have mixed up maybe a common mistake of one ? Anything can help

Disconnect the temp sensor on the radiator and see what the gauge says. If it is still pegged hot then there is a short somewhere I'd guess.
You should also check the pinouts for all of the engine bay connectors and see which might be different.

The manual and automatic harnesses might be different, I never checked but there are extra signals for an auto so it is likely different and BMW does not just use a "one for all" like domestics, there is a specific harness for each set of options (like there is no fog light wiring in cars that were built without fog lights).

Good Luck.