99 "No Cluster Bus Messages" Code, Gauges Work

[vito2772]

Hello All,

Recently my "airbag" light came on. Not after any repair or damage, just randomly.

First thing I checked my airbag connectors to the main module in the front of the dash, all looks good. My horn and blinkers work fine, so I don't suspect the clockspring.

I finally got my hands on a OBD scan tool, and I read PCM Code P1687 "No Cluster Bus Messages".

My gauge cluster is functioning normally, no other lights on expect for the airbag light.

I removed the gauge cluster and cleaned the terminals and applied some dielectric grease with the same result.

Anybody have any ideas on this? Any input would be greatly appreciated.

 

[vito2772]

"No Cluster Bus Messages" is what my scanner said. After looking up the code in the manual, it says the following:

P1687: No MIC BUS Message- No CCD/J1850 messages received from the Mechanical Instrument Cluster (MIC) module.

My next step is to check continuity from the two cluster connectors to airbag control / PCM...

 

[CharlesHS]

Remove the 32 pin wiring harness connectors from the ECU and check the pins and clips for oxidation buildup.
Inspect the wiring harness that runs along the firewall is routed behind the right rear corner of the valve cover and the threaded head stud.
The threaded head stud is known to wear thru the plastic wire loom and wiring harness insulation causing the ECU communications to short to ground.

 

[vito2772]

Disconnected battery and disconnected all connectors on PCM. Connectors and pins looked amazing, no corrosion at all.

Inspected wire harness's along firewall and behind dash, everything looks clean.

I did continuity tests on the CCD bus + and - from the PCM connector to the instrument panel and had good conductivity. I also checked the same 2 wires to ground to see if it was open to ground anywhere, it was not. And the grounds off of the instrument panel are clean too.

Kind of lost on what to do next, possible fault instrument panel? Even though everything is working besides this airbag light?

Again, the code states that there is no CCD communication between the PCM and the instrument panel. Driving me nuts

 

[vito2772]

Figured I would provide an update for any others that experience a similar issue. Turns out my Airbag control unit itself internal faulted, causing all the symptoms above.

I ripped apart the whole dash testing connectors and wires, the problem was sitting at the bottom of it laughing at me the whole time.

 

[TJ Jim]

Figured I would provide an update for any others that experience a similar issue. Turns out my Airbag control unit itself internal faulted, causing all the symptoms above.

I ripped apart the whole dash testing connectors and wires, the problem was sitting at the bottom of it laughing at me the whole time.

So where did you find a replacement airbag control unit? Or what have you done to clear the airbag fault?

 

[jonny jeep]

When I needed an ACU due to an internal fault I got one off ebay.