The check engine light comes on as I am driving along. No prob for the first couple of days. It flashed on for 15 seconds, then went off for 15 minutes and continued like that for a week. I was in no hurry to fix it, it was in the teens every day that week.

The water temp gauge got hot one day, so I took it to a buddy with a Snap on computer check. It said something about the tps (whatever that governs, I don't have a clue) needing adjustment...

Antifreeze was low, so we filled it to the top. Didn't do anything about the TPS yet. Well, of course, the light came on much less frequently, but I could not get any heat to generate from the heater, so.... I replaced the thermostat (not without cracking the housing in 5 degree weather first) well, fixed all of that, and have heat, but the light continues to come on for short periods of time and very infrequently... say, maybe once for 15 seconds every 40 miles or so.

Here is my question: what the heck does the computer (check engine light) actually govern?

Also:
Is the list the computer governs actually a mile long?
Would the Snap on computer check tell me about things like the O2 sensors and all that?
Could the faulty thermostat be the reason the Check Engine light went on originally?

And lastly:
Is the TPS a pricey gadget to fix?

thanks a million guys.
familyman

 

Ok , What engine , Yr etc etc is your truck ? To the best of my knowledge the Tps Sensor in the later model trucks is non adjustable . Tps = Throttle position sensor , It basically relays info to the Ecu on the position of the throttle . Depending on the engine in your truck there is a test to check that the sensor is defective . Visually check that the throttle linkage moves freely , ensure the sensor is seated securely & that its wiring is secure . The cooling / heating problem wouldnt cause the Ecu to store a fault code for the Tps . The Ecu is your truck engine's brain ...It recieves data from all the various sensors & controls the engines functions . The check engine light is the Ecu's way of saying something isnt within the parameters for normal operation & you or a tech needs to have a look . The Tps isnt a particular expensive part the best I recall , But do a few simple tests or have someone test the sensor to ensure its the cause of the problem .

 

Without knowing your engine and year it is difficult to help. My throttle position sensor (TPS) would be about 70$ (may be different depending on engine and year). Some of the mechanical sensor's are very easy to test, though.
Generic (potentiometer-type) sensor test: Take the sensor off (should be easy with most of them). Use a Haynes or Chilton manual (20$ - well invested) and a multimeter (9.99$). Move whatever the sensor uses to check the position of the throttle/valve/etc. and check for the appropriate resistance according to the manual.
Haven't done it on a TPS, yet (I will on sunday), but it worked piece of cake on the EGR valve position (EVP) sensor.
Of course, with some sensors you could test them without the removal, but for me it's always been more convenient to sit down with the manual on my lap while doing that (especially if it's cold outside).

 

oh, yes and you might want to check out
http://dalidesign.com/hbook/eectest.html
for a description on how to read your codes without a reader...

 

sorry guys, and thank you.
it is a 93 F 150 with the 300 straight 6 cyl. fuel injected.

well, it is 10 degrees out (heat wave!) but even so, I'm not gonna brave it. All those letters befuddle me. If my pal doesn't remedy it for me, it gets electrical tape! :-)

thanks again,
familyman

 

oh, one last thing, I also have .... uh.... that one inch diameter that goes from the engine? to the Cat has detached from the cat connection. It is not deafeningly loud, but could that cause the check engine light?

thanks again again

 

definitely! Put it back on and let us know what happens.

 

crap, I left out a word! it is a 1" diameter PIPE .... I think it is some sort of breather pipe for the cat or visa versa... maybe a breather for the intake manifold.

thanks.

will report back.