trip temp. indication

[RKHebert]

after recent pcm replacement trip computer outside ambient air temp. indication is almost always 4-8 degrees higher . relocated sensor same result. also takes approx. 10 secs. after start for voltmeter to come up to 14v. didn't really notice either indication before. anyone know if these are normal? or is new pcm defective? fyi, pcm failed at 7400 mi. took 2 wks. for dealer to get pcm. don't really want to take it back, however do want it right. thanks for any help!

 

[Alan Reagan]

That is not normal for the voltage to take that long to come up on the meter. At a minimum I would take it back and have the codes checked to make sure no fault is set.

 

[Shovelhead]

Voltmeter delay is probably caused by the grid heater cycling.



Ambient air temp is monitored by a temp probe located behind the grille, it may read a little higher due to heat from the engine, or the pavement.

 

[Alan Reagan]

Grid heater shouldn't be cyclying if the temp is above 60*F. When you same "come up" to 14, do you mean from zero or from maybe 12V. If it is coming up from 10 or 12 volts that is normal after starting for the voltage to be low during the start/charge cycle. Sorry if I misunderstood.



Do a search on the TDR. The OAT sensor reading high/low has been discussed before.

 

[RKHebert]

i appoligize for any confusion. the voltmeter comes up from approx. 12v to 14v after start in approx. 10 secs. texas heat i don't think heaters cycle as low temp. around 80 deg. as for the temp. ind. did search. read previous posts, but other's seem to report closer temp's. my previous rig was a 1500 4x4 w/ 360. it was always within 1 deg.

 

[Pete Peterson]

Not sure if your PCM is bad again or not, you really need the dealers equipment to test it.

The temp probe on these truck is in a place that will allow it to vary alot, mine varies 3 to5 degrees depending on traffic or weather I'm sittting in trafffic or driving.

Maybe the pros will come out of the woodwork on this one, it will be interesting to follow this thread... ... ... ... ... ... ... Pete