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Repair Questions and Answers.

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 #395806  by menotu
 
Chrysler 300m 2004.

While driving I had for 2-3 seconds a "no bus" fault on the Instrument cluster with ABS and TRAC OFF light coming on.

cluster comes back to life and now the ABS and TRAC OFF light stays on, even after disconnecting battery over night.

I checked the incar ABS fuse and the two ABS fuses outside, they are ok.

I read, that the ABS will delete a temporary fault after ~3500 miles, but so long I cant wait.

With Android torque there is no fault Code visible, because they are stored in the ABS Block. So only chance is a VCI POD with DRBIII correct?

Are the 4 wheel speed sensors checkable with a Multimeter?


I think this is speciality because the short no bus Information, on the forum the wheel speed sensors going faulty without no bus, so I think it's a bad ABS ecu.
Yes, I checked the socket on the ABS unit.

Oh and yes ABS is really not working.
Voltage is 13.6v and battery is fully charged and 6 month old.
 #395818  by rustybronco
 
Some aftermarket OBDII devices will scan ABS and SRS codes.

Although I have never tried it, wheel speeds sensors should be able to be tested using a multimeter. Personally I would use an oscilloscope as I have one.

I would do resistance/ voltage checks on the wiring for the ABS ECU before I would condemn the ECU. Diagnostic subroutines should be in the chassis diagnostic supplement. It might be able to be utilized without having the DRBIII. I haven't spent the time to read all the way through it but on face value you should be able to do the resistance checks.

Shop manual says 3,500 miles and the codes will be erased.
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 #395821  by FIREM
 
Wheel sensors on our cars are 2 wire magnetic pulse generators AKA MPU.
They are easily checked with a multi meter
OHMS Checks:
Both wires must be open to ground (OL most meters)
Wire to wire should have some resistance (value unknown but all should be similar)

Meter set to A /C voltage. Should generate A/ C milivolts as wheel is spun. Faster spin, higher volts
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 #395822  by TrepKing95
 
No sense in wasting time inspecting Wheel Speed Sensor signals just yet... You need to get codes checked first. If the ABS module won't talk to the scan tool, unplug the ABS Module Connector in the left front corner of the car, and check for battery voltage, ground, and PCI bus activity. It's possible that the PCI bus wire to the ABS module failed and briefly made a short circuit to power or ground when it opened which temporarily took down the whole network, but now is incapable of communicating with the ABS module
 #395854  by menotu
 
so I organized a Launch CRP919E PRO Scanner and it showed me that the rear left sensor is shorted to ground.
I disconnected it ,
and made a flying cable from faulty right side sensor to the left sensor ecu wiring, to see, if the wiring to ecu is okay and sensor faulty or wiring and now the fault was on both sides.

making a flying cable from left sensor to ecu wire of the right sensor and checked again. fault on right side was gone.

now, I know, for a > 2002 year 300M the wheel speed sensors are rare.
I made a parallel line from left sensor to right sensor, and the faults are gone. ABS working. I know, left and right rear wheels have now same speed, was in sharp curves can activate the abs. but ok.