Roler

97 Cherokee 4.0 ltr 6 cyl auto (RHD)Lately, engine temp gauge indicator doesnt want to come up or does intermittently and then drops all the way down again. when functions, holds steady in middle of gauge (no overheating)Nil other gauge issues, engine runs fine, no associated issues, grounds clean and tight. About to change out the waterpump since leaking from weephole, no overheating.Checked sensor itself, cleaned and re-attached, still does it. Feels very much electrical in nature. Had this some months ago, resolved and now returned.Is there a way to maybe test for continuity of the wiring or something, to check this issue further?Thanks in advance for your help.

Roler

No reply, that unusual. Anyone?

CCKen

You can perform the instrument cluster actuator test. This will test the CCD Data Bus and the cluster. The cluster instruments are driven by the PCM through the CCD Data Bus.

When doing the test, watch the coolant temp indicator. It will cycle through specified calibration points every 2 seconds. 100*F 2 seconds-2 seconds, 210*F 2 seconds-2 seconds, Full Scale 2 seconds-2 seconds, back to 210*F, then back to 100*F. If the indicator functions in this manner the ECT sensor or its wiring to the PCM may be bad. If the temp indicator is erratic the indicator itself may be bad. You can remove the instrument cluster and check the security of the temp indicator attachment.

If the test works out okay, try wiggling the wiries at the ECT sensor and see if the temp jumps around. If so there's a wiring problem.

The actuator test:

Instrument Cluster Actuator Test

(1) Begin the test with the ignition switch in the Off position.

(2) Depress the trip odometer reset button.

(3) While holding the trip odometer reset button depressed, turn the ignition switch to the On position, but do not start the engine.

(4) Release the trip odometer reset button.

(5) The gauges should cycle through their ranges, stopping at intermediate readings, going up and going down, at two second intervals. The indicator lamps should cycle on and off.

(6) The instrument cluster will automatically exit the self-diagnostic mode and return to normal operation at the completion of the test, if the ignition switch is turned to the Off position during the test, or if a vehicle speed message indicating that the vehicle is moving is received from the PCM on the CCD data bus during the test.

Roler

Thanks CC for your advice. (ECT= engine coolant temp?) Will try this when home.
Do I understand correctly that this ' self test' kind of tests the " pathway" from the PCM to the cluster? So, if that works, the fault lies in the pathway between temp sensor itself and PCM?

CCKen

ECT does mean Engine Coolant Temperature. THe sensor is on the Thermostat Housng.

This is from the FSM:

The instrument cluster actuator test will put the instrument cluster into its self-diagnostic mode. In this mode the instrument cluster can perform a selfdiagnostic test that will confirm that the instrument cluster circuitry, the gauges, and the CCD data bus message controlled indicator lamps are capable of operating as designed. During the actuator test the instrument cluster circuitry will position each of the gauge needles at various specified calibration points, and turn all of the CCD data bus message-controlled lamps on and off at specified time intervals.

Successful completion of the actuator test will confirm that the instrument cluster is operational. However, there may still be a problem with the CCD data bus, the Powertrain Control Module (PCM),

If an individual gauge does not respond properly, or does not respond at all during the actuator test, the instrument cluster should be removed. However, check that the gauge mounting screws on the instrument cluster electronic circuit board for proper tightness before considering instrument cluster replacement. If the gauge mounting screws check OK, replace the faulty cluster.

Roler

THanks a lot man, this is very clarifying.

blair

What was the outcome of the cluster test/your troubleshooting?
I'm having a similar issue with my 98 XJ after replacing therm stat twice and head gasket; was working great since first week of May up until last week.
I also get the feeling that my RPMs sort of float/take a few extra seconds to come down after releasing the accelerator since this started.
Heat still works great, MPGs seem to have dipped a bit though.

jalvarado8

Did you ever figure out what the issue was with your Jeep? I am running into this issue currently.

Thanks

cruiser54

This thread is 10 years old. Glad to see you used the Search function, but it would be best for you to start your own thread at this point.

Outlaw Star

Yes, Welcome to CF. Sadly, if a thread is over soo many months to years old, you won't get the answer or reply that you are looking for. Please feel welcome to make a new thread to get a faster response. In doing so, you will also meet and converse with others who share similar interests in our hobby. Good Luck.