ABS, PCM Fault code 4205, front left speed sensor

2003 911 Turbo. I have been struggling with an ABS / PSM fault code, 4205. Front left speed sensor wire, open circuit / short to ground / short B+. I messed up the front left speed sensor/brake wear harness that is fastened to the wheel carrier while trying to remove it. I removed the nut and screw holding the harness to the wheel carrier, but unfortunately, while trying to take the harness off the stud, the molded in metal part of the harness was left seized on the stud sticking out the wheel carrier. The harness was damaged with cut wires visible. ABS light and PSM light came on when I started the car. I purchased the OEM harness repair kit and had a local shop install the repair kit. Unfortunately, ABS light and PSM light did not turn off. They could not clear fault code. So I have been trying to figure out what is wrong before trying to cut into the wiring using reference material I found regarding fault code 4200. Any suggestions or ideas are welcome. Thanks Plug at PSM control unit Pins: 12, front left speed sensor signal, 28, front left speed sensor ground 15, front right speed sensor ground 16, front right speed sensor signal Step 1, 2, 3, 4: I am pretty sure that I am OK for these steps. Tried a new speed sensor and fault did not clear. Step 5 Voltage between PSM control unit and ground: Multi meter connected to pin and negative battery terminal, ignition on, measuring voltage. Pin 12 and negative, 0.004v. Pin 28 and negative, 0.003v. Pin 15 and negative, 0.003v. Pin 16 and negative, 0.004v. All less than 0.3V Step 6 Resistance between PSM control unit and ground: Multi meter connected to pin and negative battery terminal, ignition off, measuring resistance. Pin 12 and negative, infinity. Pin 28 and negative, infinity. Pin 15 and negative, infinity. Pin 16 and negative, infinity. Step 7 Resistance between PSM control unit and speed sensor: Multi meter connected to pin and speed sensor, ignition off, measuring resistance. Pin 12 and left VS, .001 ohms Pin 28 and left VS, .001 ohms. Pin 15 and right VS, .001 ohms. Pin 16 and right VS, .001 ohms. Step 8 Resistance between PSM Plug Multi meter connected to pins, ignition off, measuring resistance. Pin 12 and 28, infinity. Pin 15 and 16, 1.6 ohms on 2K setting. Not sure of this one, pin 15 and 16 are related to passenger side and fault code is for drivers side....plus I don't like what the solution may be.

Ideas?

Step 8 1.6 ohm reading is actually 1.6k ohm (since meter was in 2k setting). 1.6k ohm seems to be the internal resistance of the right speed sensor. I assume you did not unplug the right speed sensor when the measurement was taken? If so, the right side reading is expected. All your other readings look normal like you said so it's a head scratcher. Can you try measuring the resistance of the two pins of the left sensor? Should read 1~3k ohm. Also with the left sensor plugged in and the PSM unplugged, can you check the resistance between pins 12 and 28? Should read the same sensor resistance.

Thanks for reply I will check these out ASAP.

If the resistance between pins 12 and 28 is close to 1.6k ohm (with the sensor plugged in), you can check the a/c voltage between those two pins. If you hand spin the wheel, you should see something ~0.5v a/c generated. If so, your sensor and wiring seems to be fine. Steps 5 &6 you tested before confirmed the wiring is not shorted to B+ or ground.

I think I found it. Step 8, resistance between 12 and 28 should be infinity IF the speed sensor was disconnected. When I measured it the speed sensor was connected and it should have measured 1600 ohms similar to 15 and 16 not infinity. I dug into the "repaired" wiring and I believe one of the soldered connections was bad. When I cut the connection and joined it again the resistance with the speed sensor plugged in between pin 12 and 28 was 1600 ohms similar to what was measured between 15 and 16. Hope this was the problem, just need to get the fault cleared.

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Had the fault cleared and unfortunately it just came back. I am am having trouble on step 3. I don’t understand which pins are tested. Would multimeter be attached to harness pin 4 and 5 or sensor pin 1 and 2?

Drivers side sensor measured 240 mV, passenger side 295 mV. Hard to get an accurate comparison as it is based on spinning the rotor.

Same code? Where was the mV measured from? On an unplugged sensor or at the abs connector?

Yes, same code. The values above were measured at the sensors. I also measured at the control module harness, values were closer 90 mV left side and 130 mV right side. Don't get it everything appears to be ok. Left side sensor doesn’t want to come out easily, but I don’t think it is the problem. Again any help is appreciated Thanks

Lets see. Those measurements mean your sensors are good. There are no open circuits between the sensors and the abs plug pins. The only thing left seems to be short to B+/ground so I would focus on checking for that.

Is this how you would test, or should sensor be unplugged? Short to Ground Ignition off, DC Voltage between pin and battery +, sensor plugged in. Should all measure high or low voltage? 15 was .030V 16 was .024V 12 was 11.6V 28 was 11.6V 19 was 12.0 V 30 was 10.8 V 14 was 10.8 V 29 was 10.8 V. Thanks.

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12&28 should be close to 0 like 15&16. The fact that you have voltage reading between B+ and 12/28 means the 12/28 circuit is shorted to ground somewhere. You can unplug the left sensor and repeat the measurements. If same measurements, the short is within the wiring between the sensor and the abs unit.

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These were taken with the ABS side unplugged on the ABS harness side, right? It's strange that pins 14&29 (left rear sensor signal) has B+ voltage. Did you mean to measure pins 30&31 (right rear sensor)?

These are taken at the ABS control module harness in the trunk, sensors are plugged in at the wheels. Yes, I should have measure 31 and 30 instead of 19 and 30.. Short to Ground 15 was .030V, front right ground 16 was .024V, front right signal 12 was 11.6V, front left signal 28 was 11.6V, front left ground 14 was 11.4 V, rear left signal 29 was 11.4 V, rear left ground 30 was 11.0 V, rear right ground 31 was 11.0 V, rear right signal Short to B+ 15 was .001 V, front right ground 16 was .001 V, front right signal 12 was .289 V, front left signal, was much lower before. I think this is supposed to be less than .3V based on step 5, but I changed to a better multi meter. 28 was .289 V, front left ground, was lower before. 14 was .271 V, rear left signal 29 was .271 V, rear left ground 30 was .293 V, rear right ground 31 was .293 V, rear right signal Looking at the wiring diagrams shouldn't all the pins have similar measurements?

I take that "Short to B+" is test step 5? How about test step 6 - short to ground (measuring resistance)? Per the wiring diagram, if the abs side is unplugged, all these pins are only connected to the sensors and should not be connected to ANY part of the electrical system of the car. If you measure something close to B+ voltage on these pins, you have a short somewhere.

May also want to measure the resistance between the sensor pins (sensor unplugged) and chassis (in case the sensor is shorted to ground internally).

Yes Short to B+ is step 5. Did step 6 again 12 was 4 M ohms 28 was 4 M ohms All others were infinity. Going to check all again. Really appreciate your input.

Getting confused...why would the rear pins show voltage similar to 12 and 28, but no fault code?

Can you do step 6 with the left sensor unplugged and see if that makes a difference? Also check post #18 above. Unfortunately I'm as confused at this point because those pins should "float" if the abs side is disconnected. They should have no voltage.

Ok will do, but right now I can't pull sensor right now. DON"T GIVE UP! I cut wires for pin 12 and 28 at the joint created with new Porsche harness to see if voltage changed. The new repair harness is somehow showing 11.6V between end of wire for 12 and 28 in the new repair harness and + of battery. Only wires left there would be for brake wear and wheel carrier ground. Could 12 and 28 be shorting to ground through sensor to wheel carrier then to ground?

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I guess it's possible hence my suggestion of disconnecting the sensor (not removing the sensor) and test for continuity between the two sensor pins and the ground.

I replaced the wheel speed sensor. Had to drill out the old one, came out in pieced of plastic, magnet and copper wire. Voltage readings for 12 and 28 are now the same as 15 and 16. Hoping the PSM / ABS light would have turned off automatically....but it didn't. Still not sure why rear readings are different than the front.

Have you tried clearing the faults via Durametric?

Had the code cleared, but again it popped back up. i am going to start from the top.

So measured all the pins again, with sensor plugged in Step 5, short to positive. Multimeter set to measure volts between pin and negative battery terminal 15, 16, 12, 28 all measure .010 V 30, 31, 14 29 all measure .528 V. Will have to see if this changes with rear sensors unplugged. Step 6, short to ground. Multimeter set to measure M ohms between pin and negative battery terminal. 15, 16, 12, 28 all measure over load. 30, 31, 14 29 all measure 8.1 mega ohm. Will have to see if this changes with rear sensors unplugged. Short to ground. Multimeter set to measure volts between pin and positive battery terminal. 15, 16, 12, 28 all measure .100 V 30, 31, 14, 29 all measure 11 V. Will have to see if this changes with rear sensors unplugged. Before I changed the front right sensor I was measuring 11 V for 12 and 28 to positive battery terminal. I wonder if both rear sensors were messed up somehow when the harness was damaged? I think I may just pull the rear sensors and replace them.

So I replaced rear sensors. All measurements appear to be normal now. Unfortunately, abs psm lights are still on. I am not sure if they should automatically clear or need to be cleared with software.

Maybe just drive it for 20mim and see if the warning light goes away?

No luck. I will see if i can get it cleared,but I have a sneaky suspicion it will pop up again.

What error code are there now?

Cleared code. 4205 would not clear. New wiring, new sensor. What other tests can be done to ensure wiring is sound.

Had the system been working fine with no error codes before you worked on the front left sensor harness? Kind of strange you needed to correct so many things at once.

There were no issues at all before the harness was damaged.

In that case, seems the focus should be on the repaired harness, which I assume you must have gone over many times now. Those tests are quite comprehemsive and should catch any issue. I don't know how difficult it is to access the wire pins of the abs plug while plugged in but if you can back probe the sensor signal wire (or tap a wire off the signal wire somewhere) with everything plugged in and with key ON, you could check for a/c signal while hand spinning the wheel. This will test directly what the sigbal is seen by the abs unit. Can also check for short to B+ and ground the same way.

Punko - Did you ever get this resolved? Am experiencing very similar symptoms which brought me to this post. Will document my case, hopefully come to a resolution and be of help to others. Car is a 996 C2 5.7 ABS - Same issue, left side harness damaged and (RWD version) ABS harness replaced. New Speed sensor replaced. Unable to reset the ABS 4205 fault code with durametric (pro version). Dash warning indicating same. - Fault Code Tiptronic Code 25 CAN Front Left Wheel RPM from PSM implausible Real Time Data from another obd2 scanner show 4 wheel speed sensors in action and indeed Left Front showing 0 while other 3 as expected. STEPS 1-8 from Porsche Diagnostic Manual 1 - Visual Inspection: Speed sensor and leads are fine because the "last mile" Speed Sensor has already been replaced. Leads/joint on repair section double checked. 2 - Checking Speed Sensor: Resistance measures 1.7kOhm (with in 1kohm - 3kohm range). 3 - Checking function of speed sensor: Check that AC voltage approx. Same as other side. I didn't check this given sensor is new. 4 - Mechanical function: Check Speed Sensor and Toothed Ring for soiling/damage. Check OK. 5 - Checking leads of Speed Sensor for short circuit to B+: Voltage Both Pins 0.0~0.01V (with in <0.3V range). 6 - Checking leads of Speed Sensor for short circuit to Ground: No Continuity from PSM module pins for signal/ground to Common Ground. 7 - Checking leads of Speed Sensor for Open Circuit: Continuity from PSM module pins for signal/ground to respective speed sensor signal/ground. (Question: Step 7 - PIN 4 and 5 refer to the speed sensor harness male pins... and speed sensor PIN 1 and 2 refer to the female pins on the speed sensor side?) 8 - Checking leads of speed sensor for short circuit with respect to each other: No Continuity. 9 - Replace Speed Sensor Left - Already done before test 10 - Replace PSM Control Unit ... Does the manual mean replacememt of the ABS Pump module or PSM ECU here? This reference to a similar description where the ABS harness was damaged, and OP claims damage to module occurred. Is this common or plausible? https://www.renntech.org/topic/31619-abspsm-module/ Thanks!

Don't you just love reading a long story with no end...

Well it ended up being the control module. I sent the module to a local electronics repair shop and they said it could not be repaired. I ended up replacing the module with a used one from a wrecker and magically the lights all went out.

The wrecker sent me the control module and abs pump all as an assembly.

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Was afraid of that... Thanks for the update and confirming.

Searched but can't find an answer. Can anyone confirm whether the PSM control unit needs to be re-coded or is paired with any other devices such as the ABS pump or main DME? In other words can a used unit plug and play? Thank you

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Glad you got it sorted. Who would have guessed it's the controller because you had mentioned the light came on after you damaged the speed sensor/harness. That's quite a coincidence.

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Exact same situation here, except with a c2. Coincidence or could damage (short) to the harness damage the controller?

I think damaging the abs wiring harness resulted in a short screwing up the control unit. No coding was required when I replaced the control module. The entire abs assembly had to be removed to access all the cap screws that fasten the control module to the pump. Plug and play.

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Thanks Punko, is that the reason for replacing the pump and ecu as a set? Information I've been told is PIWIS programming and adaptation required, if changing just the Control Module.

No, I didn’t replace the pump. The pump had to be removed to access the cap screws that fasten the control module to the pump. I couldn’t find anyone selling just the control module. No no programming was required. Thanks.

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I may be getting 2 different parts confused. The diagnostic manual, step 10 of 4205 states to replace the "PSM control unit" I thought this was the ECU. Is my understanding correct that, you changed only the circuitry control portion (black housing) of the ABS hydraulic module? Thanks Punko ABS Hydraulic Pump PSM Control Unit

Yes I only changed the black housing in the first picture.

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Thanks for your reply. Trying to reconcile what seems like conflicting points - Step 10 of the diagnostic manual calls for replacing the "PSM Control Unit". 4205 has 2 solutions, replace the left speed sensor or replace the PSM control unit. If my info is right, the 996.2 5.7 ABS do not have the PSM ECU as a separate ECU but is integrated inside the DME. Is this a typo in the manual, and they are actually referring to the module contained inside the black housing? Thanks!

The instructions refer to the plug on the black box as the psm control module plug.

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Thank you Sir!

I found it quite interesting that damaging the harness could damage the control unit given that the control unit is supposed to be able to detect short to battery "+" or short to ground, etc. You would think for robustness, the control unit should at least tolerate any shorts introduced by the sensor wire harness.

When I get a chance I plan on opening up the black box...maybe I can see what the specialist said can’t be repaired?

That would be interesting to see and learn.

I have the same issue. I replaced the suspension on a 2004 C4 S 6s. When I got it back from the shop the ABS and PSM lights were on. The technician could not find any issues. I had another shop look at it and they believed that the front left wiring harness had a short. They repaired that, but it did not change the lights. They recommended replacing the ABS module. I purchased a replacement from eBay from a similar 2004 C4S. Connecting it gave the same error suggesting that this was a wiring problem. The technician had a new ABS module in the dealership and said that when that was connected it solved the problem. I had the local ABS shop take a look at the eBay ABS module and confirmed that it was a good module. We’ve now replaced the left wiring harness and run through the steps above to test for shorts. It makes no sense to me that the original ABS module and the eBay ABS module are both showing faults with a new ABS module does not. Is there any programming that we need to do to the eBay ABS module for it to work?A new module is horrendously expensive.

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Exact same story line. About to choose the 2nd hand route also... Sorry to hear about your problems. Would be great to get to the bottom of this. Did the module part # match the old one? Conflicting info on whether calibration/coding is required on replacement new/old. Did you ask the dealership tech whether he had to code the new ABS module that resolved the issue? thnx

For my situation, no programming was required. Perhaps find another used module?

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I'm not a service tech, but Porsche tech 3 is and he stated in one of his posts that an ABS from a tip will need to be calibrated using PIWIS to work with a manual tranny. They are interchangeable otherwise.