88 dodge ram d100 w/ 318. code 22 = coolant temp sensor out of range. replaced with a non oem coolant temp sens. I bought off ebay.....still have code 22. any ideas?? I have disconnected and reconnected while checking timing...will this produce a 22? Do I need to disconnect/reconnect battery every time I mess with it to reset the codes?? Also, I have a code 24 now..... thx, mike

 

Sounds like the problem is somewhere else in the circuit and not the actual sensor. To double check the sensor, make sure its cold and check the resistance. Cold (50-80 degrees F) should be 17,900 to 10,800 ohms and hot (180-200 degrees F) 1170 to 820 ohms. Then backprobe the connector and check for reference voltage with the key on engine off. It should be around 5 volts. A code 24 is your throttle position sensor. Check for reference voltage on the TPS by probing the purple/white wire and the black/blue wire. Reference voltage that is also 5 volts. To check the TPS signal voltage, probe the orange/blue wire and the black/blue wire. With the throttle fully closed, signal voltage should be from .5 to 1.5 volts. Slowly open the throttle and watch the readings. At wide open throttle the voltage should read between 3.5 and 4.5 volts. If it doesn't, the TPS is bad.

 

Yes you do have to disconnect the battery every time to clear codes or cycle the ignition 50 times. The chance of 2 sensors going bad at the same time are not great, so I would think you have a bad ground to the manifold or your signal voltage to the sensors is off. Install a temporary ground to the manifold and clear the codes, start the truck and let it warm up then shut it off and check the codes. While it is running you can check the feed voltage to these 2 sensors.

 

The voltage w/ the key on and engine off is 4.91 volts, resistance on the new coolant temp sensor is 7.9k ohms....of course, it is about 90 degrees outside today, but that seems well out of the acceptable range.....are you sure on the resistance ranges?? the old temp sensor reads about 7k ohms.....

 

Just checking the connector voltage (unplugged from the TPS), I am getting 4.4 volts....what is the recommended procedure for checking these voltages while it is plugged in?? I do not know how the TPS works - if it is basically a potentiometer (variable resistor), maybe there is a resistance range that can more easily be checked while it is unplugged??? thx, mike

 

The TPS is a potentiometer. Having the correct voltage at idle and WOT does not mean the TPS is good. The change in voltage must be smooth between these 2 points or drivability symptoms will show up. All voltages are checked with the sensors plugged in. You can use paperclips to back probe the connecters and clip the meter to. I have never found the resistance specifications for the TPS and if you find them please share the info.

Check the reference voltage at the computer itself on pin 13 of the 60 way connector and compare to what you are getting at the TPS. It must be 5 volts.

 

I've misplaced my Haynes manual, but WHEN I find it (and it better be SOON!!!) I will check the voltage at the computer. Is there a separate device that produces the 5 volts that might need replacement?? Is 4.9 volts at the coolant temp sensor acceptable?? thx, mike.

 

The computer generates that 5 volt signal internally. Meters are not totally accurate unless they are in calibration.

Have you tried grounding the intake manifold to rule out a ground problem? It is not usual that you have 2 sensors go out at the same time.

 

Not sure what you mean by "ground the manifold" - run a separate wire from the stud to another part of the block?? I DID, however, take the existing ground off of the manifold, clean up the connection, and tighten it back down. I then compared the resistance of just the wire (not connected to the battery OR the manifold) to the resistance from the battery end of the wire and (w/ wire connected to the manifold) a point on the engine block.....they were the same.

The truck seems to be running a bit better with each little thing that I do to it.....replaced cap and rotor button yesterday - idles a bit better now.

I DID find my Haynes manual, finally.....has anyone had any experience with "worn cam lobes"??? How would I rule that out??