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ABS, PCM Fault code 4205, front left speed sensor

 
Old 07-26-2018, 08:42 PM
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Punko
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Default 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.










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Old 07-27-2018, 09:04 PM
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Ideas?
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Old 07-31-2018, 02:56 PM
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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.
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Old 08-01-2018, 06:21 PM
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Thanks for reply I will check these out ASAP.
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Old 08-02-2018, 05:31 PM
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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.
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Old 08-03-2018, 08:20 PM
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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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Old 08-03-2018, 08:33 PM
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Old 08-10-2018, 06:51 PM
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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?

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Old 08-11-2018, 01:12 PM
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Drivers side sensor measured 240 mV, passenger side 295 mV. Hard to get an accurate comparison as it is based on spinning the rotor.
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Old 08-11-2018, 02:58 PM
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Same code? Where was the mV measured from? On an unplugged sensor or at the abs connector?
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Old 08-11-2018, 04:08 PM
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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
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Old 08-11-2018, 04:13 PM
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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.
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Old 08-12-2018, 09:23 PM
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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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Old 08-12-2018, 10:32 PM
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Originally Posted by Punko View Post
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.
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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Old 08-13-2018, 02:00 PM
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Originally Posted by Punko View Post
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.
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)?
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