cameronc56

Car's back with a new alternator, the battery's charging to full now and the dash lights are all off except for one - The PSM light is turning on after driving up to 10-15 mph. Any ideas?

996love

I have no clue. It could be a wheel speed sensor, or maybe a steering angle sensor (do our cars even have those?)

Is the light off the next time you start the car, but re-illuminates as soon as you go over 10-15mph?

If the light doesn’t ever go away, you could try to force it off by disconnecting the battery. I like to remove both the positive and negative cables from the battery terminal, and touch them together for about 30 seconds. (Just the ends of the cables only!)

Then you reconnect the cables to the battery and see if that changes anything. If the light no longer appears, it likely means something was temporarily disconnected while your car was being worked on, but was corrected afterwards.

If the light still shows up, then the car has an issue that needs to be addressed. At that point, you’ll need a proper scan tool (like Durametric or PIWIS) that can communicate with the PSM module to identify the problem.

cameronc56

Thanks for your help, its turning off after restarting the car then turning on again. Most of the wheel speed sensor threads ive been reading have both abs and psm lights coming on. I just bled the brakes and made sure they were all connected and didnt see anything wrong

I have a durametric, i just need to get a windows laptop to run it on. I'll try to use that to investigate once I'm back from a roadtrip I'm doing in the car this weekend. Hopefully no other issues pop up on the road

theprf

Unplug and replug the pressure sensor. It's either on the ABS unit or the PSM pump. It's got a little 3-wire plug.
A tiny bit of corrosion can get into the plug and mess up the pressure reading. Unplugging and replugging wioes any corrosion away.

cameronc56

No luck unfortunately

theprf

Brake light switch is a common problem too.

cameronc56

I replaced that soon after i got the car 6 months ago because the psm/abs lights were coming on. But that was a lot more irregular than this, sometimes it wouldnt come on at all, and it seemed to be triggered by braking... replacing it fixed that issue

cameronc56

alright i finally got a cheapo windows laptop for the durametric. p0153 and p1119 are still stored, along with abs code 4480, which is likely the reason for psm coming on. I reset that ABS code so hopefully it doesn't come back!

theprf

If 4480 returns it's probably a bad connection inside the ABS module, pretty common on the 5.8 ABS. Supposedly Module Master can fix them.

wdb

They fixed two of my BMWs. Two thumbs up.

cameronc56

just took the car on a test drive and the psm light came on again, 4480 is back. Durametric is actually saying this is the 5.7 @theprf




i unplugged everything i could get to and blew air over all the connections, the only one that looked suspect was the one plugging into the brake fluid reservoir, that had some brake fluid in the connection that i cleaned up. I havent had a chance to test if this fixed anything yet

hardtailer

(Bosch) 5.7 is correct designation, also for BMW and all other Bosch ESP of that era. 5.8 is a typo.
Do the warning lights illuminate only when driving faster than 25mph? That would indicate that the cause is to be found between booster pump, its pressure sensor and the control unit.

Quick check of the pressure sensor: across terminals 1 and 3 on the side of the wiring loom you should get 5V when ignition is on.
If you manage to supply 5V to the sensor (observe polarity, it must be as given by the wiring loom), then across terminal 2 and 1 (or 3) should read either close to 0 or to 5V when pump is not running.

You can check the pump itself by feeding it 9-12V to its wires directly. If it's stuck then you've found the cause. You can remove it and take it apart to replace the bearing that most probably is so corroded it no longer turns.
If it runs then you can check if the sensor gives a reading between terminal 2 and 1 (or 3) whilst fed with 5V. If it does, your ECU requires repair.

Search the Internet for similar woes on BMW E38 and E39, they used the same BOSCH 5.7 ESP (DSC in BMW speak, and booster pump is called precharge pump).

Make sure I identified the plugs correctly in the picture before supplying voltage to pump or sensor!

theprf

Yeah 5.7 stupid typo using my phone.

cameronc56

@hardtailer i took some measurements today

voltage of pressure sensor, ignition on, this looks right

I found the 4480 diagnostic instructions in the 996tt manual:

Following step 1, with the ignition off (or on), I'm not getting any voltage from p2 and ground... seems like a problem. This is the psm module plug, right? The schematics I'm finding online show a 42 pin connector, this one only has 15.


with the ignition on, I'm not seeing any voltage on pin 4, so thats good

I'm not sure what the non-ghetto way to supply voltage to the booster pump is, but I bought a 21/23 12v battery and just taped some wires to it. With the ignition on, it doesn't seem to do anything when i touch the wires to the pins in the connector coming from the booster pump, the one thats disconnected in the bottom picture. Could the pump be dead? Or am I doing this completely wrong

theprf

I have not seen that type of plug on a 5.7 ABS (or a 5.3 ABS for that matter).
The precharge pump takes 40 amps so your little battery won't do much. Jump it to the car battery using big wires (remember, 40 amps) just for an instant.