Hello everyone:

Vehicle:
1991 Dodge W150 5.2l 318 w/ np 435

Recently my check engine light has been on. However, it is pretty erratic and never illuminates at start up so I haven't been able to pull a code flipping the key back and forth. It is very inconsistent. Today I drove 35 miles straight without it lighting up but on the return trip it came on within 2 miles. I haven't noticed any mechanical issues.

I am not sure if this is related but it started coming on after I replaced the coolant temperature sensor, distributor cap & rotor, and PCV valve. My coolant temperature gauge still is reading zero after replacing the unit.

Does anyone have any ideas/suggestions?

Thank you

 

I think the coolant temperature sensor is one of the few items that will trip the CEL. Did you test the thermostat? Are you getting heat from the vents?

 

There are 2 coolant temp sensors. The one by the thermostat housing is for the computer and the one on the passengers side of the intake is for the gauge. Which one did you replace and are you sure you replaced it with the proper part?

 

When I turn the heat on, hot air is released - not very powerfully and it doesn't come through the vents but rather from underneath the dash assembly but that's probably unimportant.

I haven't tested the thermostat yet.

I believe I replaced the sensor for the computer then. It was the one underneath the upper radiator house and behind the smog pump bracket. When I removed it a bit of coolant flowed out. I replaced it with a part from NAPA. http://www.napaonline.com/Catalog/Ca...5SB_0331888768

I did have a little bit of trouble threading the new part in... Torqued it to 20 ft-lbs - Some threads still showing but that is how it was before. I wish I could find the old one. Dug through my waste bin and found everything from that day except the sensor.

It seems to me that I need to replace the other one then for the gauge.
Is the one for the gauge this: http://www.autozone.com/autozone/par..._77401_0_5673?

Thank your inputs and the quick replies.

 

That appears to be the correct sensor at NAPA. The auto Zone site won't come up for me.

Unless you are having problems you have not posted yet I would concentrate on why the check engine light is intermittent. I would not trust that light until you can get it to come on when you first turn on the key like it is supposed to do. Maybe the bulb is going bad (broken filament that makes contact every once in a while) or a bad connection/wiring or something else.

 

Thanks SEAL, I will look into that. It has been puzzling me for a while now but I haven't been able to discern a pattern. Once the light comes on, it will stay on for as long as the engine is running. However, as soon as I turn the engine off and start it back up, it is gone.

 

I have the same thing happening to my truck right now where the check engine light comes on randomly. I took it to my dads friends shop and had them plug it in. It turns out that it is a faulty alternator sensor. I haven't replaced it yet, but probably should soon, i currently just ignore it


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MNfarmboy: Are you talking about your 2006 or the 91?

 

I am taking about the 91


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Is it possible to to plug in the pre-OBDII vehicles into some sort of reader?