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ABS, PCM Fault code 4205, front left speed sensor

 
Old 08-13-2018, 02:27 PM
  #16  
Punko
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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?
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Old 08-13-2018, 02:33 PM
  #17  
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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.
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Old 08-13-2018, 03:39 PM
  #18  
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May also want to measure the resistance between the sensor pins (sensor unplugged) and chassis (in case the sensor is shorted to ground internally).
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Old 08-13-2018, 03:50 PM
  #19  
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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.
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Old 08-13-2018, 04:15 PM
  #20  
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Getting confused...why would the rear pins show voltage similar to 12 and 28, but no fault code?
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Old 08-13-2018, 04:31 PM
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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.
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Old 08-13-2018, 08:08 PM
  #22  
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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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Old 08-13-2018, 08:58 PM
  #23  
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Originally Posted by Punko View Post
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?
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.
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Old 08-19-2018, 05:59 PM
  #24  
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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.
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Old 08-19-2018, 06:23 PM
  #25  
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Have you tried clearing the faults via Durametric?
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Old 08-20-2018, 09:23 PM
  #26  
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Had the code cleared, but again it popped back up.

i am going to start from the top.
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Old 08-21-2018, 10:07 PM
  #27  
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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.
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Old 08-29-2018, 09:00 PM
  #28  
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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.
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Old 08-29-2018, 09:28 PM
  #29  
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Maybe just drive it for 20mim and see if the warning light goes away?
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Old 08-30-2018, 11:18 PM
  #30  
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No luck. I will see if i can get it cleared,but I have a sneaky suspicion it will pop up again.
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