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Check engine light always on.....scanned but showing no codes.

PlayvorPlayv99XJ

NAXJA Forum User
Location
Allentown, PA
My stock 1999 XJ has a constant check engine light but when scanned shows no codes. I need to get it inspected but im at a loss on how to get the light to turn off. Any help would be greatly appreciated. Thank you guys
 
Disco the battery for a few minutes, then hook it back up. That should clear any codes.
 
I tried disconnecting the battery to reset everything but the light remains on. I dont have my own personal scanner, I took it too a dealership and had them scan it for me. Seems like some kind of dumb electrical wiring issue to me.
 
It is a simple issue to figure out, with a scan tool.

Scanning data should show whether or not the ECM is requesting the Instrument cluster to turn on the light.

If the ECM is not requesting the lamp on, then the IC is faulty.

If it is, and there are no codes associated, then the ECM is faulty.
 
You could perform this test to see if the intrument cluster is driving the CEL properly.

As the cluster goes through its presets, the CEL will come on for 4 seconds, go off for 2 seconds, then back on for 2 seconds, then off again. If the CEL remains on all the time the instrument cluster may be at fault.

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 (RUN) 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.

 
Thank you Digger87xj and Sidewinder CC. I am about to go outside and work on it a little bit and will try these thing you mentioned. I will post a reply later in the day with an update.
 
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