"CHECK ENGINE" Light

[BLUEDOT 72]

Is there any place that I should start looking when my "CHECK ENGINE" Light came on. This on a 1998, 12 Valve, Calif. Emmision, 2500-4x4. with about 86,000 miles. Or is this just a notice to take it to the dealer? I'll apprecaite any advise I can get---Thanks... . Jim

 

[HoleshotHolset]

Maybe the magnetic reluctance sensor near the harmonic damper..... it senses engine rpm.



Hrmm... see that's the problem with these 12-valves no sensors to mess up!! (wait... that's the GOOD part about these!!)



Other than that... . the throttle position sensor, coolant temp sensor, manifold temp sensor... . there really isn't much else... . and the thing will run fine without any of them even connected... . the ECM just likes to know what's going on... that's all. The throttle position sensor affects the transmission, but you didn't say you had probs with the transmission... .



I'm not sure if the 'check engine' light would come on if there was a problem with the transmission..... '96 and up trucks have all electronic trannies... .



Matt

 

[PHaller]

check engine light on the 12 valvers

On the 2nd generation 12 valvers the check engine light is only a sentry to alert you to an out of compliance occurance. Most of the time it's an EGR related issue but it could also be a transmission issue. The 12 valved trucks PCM have NO control over motor function and can only alert you.

I would run a PCM code check by cycling the ignition switch 3 times within 3 seconds and then leaving the truck in the ignition on state. The PCM will deliver the codes through the check engine light. Write down the codes and check them against the manual. There are a lot of different codes but 55 will always be present along with various others. 55 means end of list.

My guess is you have a bad EGR or intake air sensor failure or a transmission lock up overvoltage, if you have an auto. The codes will at least point you in the right direction. Disconnecting the batteries for 15 minutes will clear the codes stored in the PCM. Clearing the codes will leave you with another code for 200 key cycles that you disconnected the batteries within the last 200 key cycles.

-Paul R. Haller-

 

[HoleshotHolset]

Yeah... . what Paul said.



Matt