Mysterious CEL -- 2001 Quad Cab 4X4 4.7L

[redundant2]

Just got a CEL (Check Engine Light) on my 2001 Quad Cab 4X4 4.7L V8 with 65,000. Original plugs and wires, and slightly overdue for an oil change (time not miles, since I usually only put 1000 to 1500 on every 3 months or so)

Truck runs fine.

A couple weeks prior to this CEL I changed the Throttle Position Sensor because of a bouncy idle (no CEL at that time). New TPS fixed the bouncy idle and it is running great now.

CEL just came on 2 days ago on startup with no signs of poor performance.

I haven't had it checked for codes yet, thought I might get some ideas here before shelling out the cash just to get it scanned.

Could it be a MAF (however, no rough idle, etc.) or Oxygen Sensors or something like that?

Thanks

[vamc]

If you have an autozone by you, they can scan it for free. Just a thought.

[jlistunner]

From my Haynes repair manual for all Dakota Pickups 2000 - 2003 it notes under Chapter 6 Section 4 Throttle position sensor - check and replacement, the following. "Performing the following test will set a diagnostic trouble code and illuminate the CEL. Be prepared to clear the diagnostic trouble code after performing the tests and making the necessary repairs." Chapter 6 Section 2.38 also states the following. "Always clear the codes from the PCM (Power Control Module) before starting the engine after a new electronic emission control component is installed onto the engine. The PCM stores the operating parameters of each sensor. The PCM may set a trouble code if a new sensor is allowed to operate before the parameters from the old sensor have been erased."

This should help.

[redundant2]

Ah, yes. That is the problem. I should have disconnected the battery before changing the TPS. It looks like my truck needed to clear the "memory" of the previous TPS before it could "get acquainted" with the new one. I take it that the CEL was just telling me that something was different that it didn't recognize.

Thanks

[jlistunner]

I don't believe disconnecting the battery before you replaced the TPS would have prevented a CEL. The PCM holds the sensor's parameters in memory and since you were replacing the sensor with a new one the PCM will still use the old sensor's parameters for it. Disconnecting the battery would not have erased the PCM's memory.

[redundant2]

Originally Posted by jlistunner

I don't believe disconnecting the battery before you replaced the TPS would have prevented a CEL. The PCM holds the sensor's parameters in memory and since you were replacing the sensor with a new one the PCM will still use the old sensor's parameters for it. Disconnecting the battery would not have erased the PCM's memory.

Okay, so how exactly do I clear the PCM? Does it say anything in the Haynes manual?

[vamc]

code scanner

[bloodyprice]

yah

go to advance auto parts or autozone and theyle clear the code for free