Archived Temp Gage

[rkressg]

My Coolant Temperature Gage Has Gone Crazy:-{} It keeps going up and down. I have replaced the coolant temperature sensor 2x but with no resolve. I have checked the resistance of all sensors in water at various temps and they are all still good. I have 5. 00 volts at the sensor lead constantly. I have been getting the following codes :{ at the ECU of 117, 118 and 217. I can clear these codes and they come back. I have never been able to detect a change in voltage at the sensor, but 117 and 217 mean a low and high voltage read on the coolant temperature sensor respectivly. Also, the code 218 (Over temp condition ), the motor still holds perfect temperature of 185 but the gage says other. The truck has 38,000 miles, so am I out of luck if the ECU has gone south. Any help would be appreciated. :-{}



P. S. I love these guys :-{}

 

[wtrenholm]

That could be hard to diagnose. The temp sensor seems to be an input to the Cummins ECM, it sends the info out over the bus to the cluster, which processes the signal and drives the guage.



I would assume the bus network is ok, the rest of the cluster gets info over it. That still leaves a lot of options. I haven't played too much on my truck but if you could back probe the ECT wire into the ECM (hard to get at) to monitor what voltage is actually being seen by it. Then compare the meter reading to what a scan tool (DRB)shows for ECT voltage, they should agree. The DRB will also let you actuate the guage over the bus, but with codes in the ECM I doubt it's anything to do with the cluster. Sensor ground on the diagram is shared by numerous items so it should be OK also.



It seems like it could be a wiring type of problem with three codes setting for one sensor, or ECM for that matter. The voltage at the ECM must be floating all over the place. The drivability book may help to diagnose the codes if the problem is present when doing the routines.



Good luck,

Wayne

 

[Blair]

You are never out of luck that close to end of warranty. If you have raport with your dealer ie you spent money there on service go and see them be nice don't yell (they are human) and ask for help from them and DC. There is ways to make things happen.

 

[rkressg]

Thank you Blair,

I callled detroit and got a service ID number. I talked with a man named Larry. He said that because I had other previous computer problems, I should have no problems passing this through as a warranted repair.



I have followed all steps to remedy this problem as stated in the 2001 DC service repair manual. I have also talked with other fellow Diesel Mechanics and they said do everything I have done. These motors are different than what I am use to working on. I spent 2 years working on heavy CAT motors, and these are too small for many of my tools.



My only fear is that the ECU has bit the dust, but this problem has remained only with the Coolant Temp Sensor and has not affected other areas of the truck, yet:-{} #@$%!



I have an appotment with my dealership on Friday. I hope it goes well. The only modifications I have done to the truck is Boost and Pyro gages, Removed mufflers, and perminately attached jumper cables.