ABS blink test
 

Hi everyone,

I have a '92 xj6 sovereign with an "anti lock" light on in the dash. There are no codes showing on the VCM and all fuses are intact. I am trying to conduct the blink test and found the directions but do not know what the PM4 connector is. If someone has a picture and can direct me, I would appreciate it.

Also while I was looking around the area, I found several connectors without a mate. I am assuming these are for diagnostic purposes but thought I would double check. In addition, I am getting water inside the drivers taillight assembly even though I have sealed the assembly, lens, removed the trim along the middle of the rear bumper and sealed there too. I'm just not sure where the water is coming in - any suggestions would be appreciated.

Thank you - William

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The Diagnostic Socket is located LEFT FRONT CORNER OF TRUNK.
4 wires have colors as follows..NP, RB, NK, B.

DO NOT touch the RB to anything!!!!!!!!!!!!!!!!!!!!

I think the B and NK are the wires to short together but it has been over a decade since I have done this.

bob

Thanks Motorcarman,

I found the PM4 Connector and attached a picture (brown socket). It is directly above and slightly forward of the ABS ECU on my car. I received the following codes: 21, 33, and 43. Anyone able to decipher those?

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Please see attached PDF.

21 - Main Valve Failure (Defective valve, cable harness, power transistor in ECM)

33 - Rear Right Sensor Failure (Recognized by Trigger Monitoring)

43 - Rear Right Sensor Failure (Recognized by wheel speed comparison)

-Nick

Thanks Nick.

I pulled the rear sensor, cleaned it and inspected the wire. Other than some failing insulation it appears intact. I patched that up and put everything back together. After driving the car for a period of time, the abs light is still on. I was thinking of replacing the wire for the sensor in case its broken inside - I'm not sure about checking for continuity unless I peel back some insulation near the sensor itself.

Is there anything else I should be checking outside of that sensor? I feel like all three codes point toward the same thing unless 21 can imply something else.

Thanks again for the help.

21 would be pointing to the main valve which operates during ABS operation. IIRC, it allows pressurized brake fluid into the front brake circuits to keep the brake pedal from sinking during application. I'm not sure if the valve is serviceable separately.

As for the wheel speed sensor, I'm gonna guess it's either dirty or defective. The only other common issue is a wiring fault. You can check resistance right at the ABS module connector. You should see 0.8K - 1.4K ohms between pins 27 and 45 (right rear).

You also do a voltage test too. Raise the car and allow the wheels to hand freely. Ignition Off. Spin the Right Rear wheel at 1 Rev per second. With your meter set on AC Voltage, measure between pins 27 and 45. You should see 0.04v - 0.1v AC.

The sensors aren't cheap. May be best to find a salvage yard similar to "Pick-n-Pull" we have here, and grab all four for spares.

-Nick

21 would be pointing to the main valve which operates during ABS operation. IIRC, it allows pressurized brake fluid into the front brake circuits to keep the brake pedal from sinking during application. I'm not sure if the valve is serviceable separately.


Thanks for the information Nick. I placed some calls to local salvage yards regarding the sensors. In the meantime, I am having difficulty locating the main valve that's associated with code 21. Is that the unit that sits below the accumulator ball in the engine bay?

Thanks