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Dr. Hamman
Dr. Hamman, Chevy Technician
Category: Chevy
Satisfied Customers: 5786
Experience:  30 Years Experience repairing, customizing, and building chevys.
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2001 chevy impala: temperature gauge..temperature sensor

Customer Question

2001 chevy impala 3.4 engine the temperature gauge stopped working and the a/c at the same time the code PO118 came on. We replaced the temperature sensor and it still the same. I replaced the sensor again and it stills the same. i read the pinout of the computer and it said that the orange and black wire should have a reference voltage. there is no voltage there. I trace the wire to the ecm and there is continuity but no voltage going through the wire. I replaced the ecm, flashed it and reprogrammed the key. The problem stills the same. All the fuses are good. The temperature gauge moves just a little but stays completely down when you first put the ignition switch on the on position. I need help finding the problem?
Submitted: 2 years ago.
Category: Chevy
Expert:  Dr. Hamman replied 2 years ago.

Hi, I am a professional certified mechanic, with an engineering background, and 35+ years experience. I will do my best to assist you today.



I am an electrical specialist, and I have dealt with a lot of problems like this before. The PCM, and the BCM are both involved with the AC system, but only the PCM deals with the temp sending unit, so if there was a module problem that could kill the function of these two systems, it makes sense the PCM would be bad. I see you have been down that road. There are a lot of possibility’s here, and this type of problem can get real deep real fast. What I have found so many times is a trouble code tells what the computer perceives to be malfunctioning, but doesn’t very often tell you why, or if the part is really acting up, just like the temp sensor, so normally I test the sensors before changing them. What I am suspecting is a possible bad connection at the PCM, or even more likely a power or ground failure to the PCM. A PCM will almost always have multiple power in and multiple ground wires. If it looses power or ground on any of it's power or ground wires it will loose partial function. Power or ground failure can be in the PCM connector, where the contacts come together, or where the connector crimps to the wire, these types of bad connections are hard to ID. I would get a complete pinout for the PCM, and verify all power and ground inputs. If you have any more questions I am here to help. Good luck with it, and Thanks for using Just Answer.


I hope this helps, 100% satisfaction is my goal. Myself personally, and Just Answer are here to serve you. If the answer is not clear, let me know what additional help you need, and I will assist you further. When you're satisfied, and feel you can leave a positive feedback please accept my answer. I don't get paid unless you do. A bonus and positive feedback are always appreciated, good luck and Thanks.





Customer: replied 2 years ago.
I HOOK THE SCANNER. I CHECKED THE COOLANT TEMPERATURE AND IT CAME UP AS A -35C THEN I PUT A 3 AMP FUSED JUMPING WIRE BETWEEN THE TWO SENSOR WIRES AND THE TEMPERATURE WENT UP IN THE SCANNER TO 140C SO THE PCM IS READING THE TEMPERATURE BUT THE GAUGE IS NOT. WHAT KNOW?
Expert:  Dr. Hamman replied 2 years ago.

Hi, I am a professional certified mechanic, with an engineering background, and 35+ years experience. I will do my best to assist you today.



If the PCM is reading the temp, and the gauge is not, I would check out the gauge, and the wiring to the gauge. Good luck with it, and Thanks for using Just Answer.


I hope this helps, 100% satisfaction is my goal. Myself personally, and Just Answer are here to serve you. If the answer is not clear, let me know what additional help you need, and I will assist you further. When you're satisfied, and feel you can leave a positive feedback please accept my answer. I don't get paid unless you do. A bonus and positive feedback are always appreciated, good luck and Thanks.





Customer: replied 2 years ago.
WOULD YOU CHECK IF THE SIGNAL GOES FROM THE PCM TO THE GAUGE OR HOW DOES IT GET THERE?
Expert:  Dr. Hamman replied 2 years ago.
Let me check that out for you.
Expert:  Dr. Hamman replied 2 years ago.

Hi, I am a professional certified mechanic, with an engineering background, and 35+ years experience. I will do my best to assist you today.



OK, I checked it out for you, and it is complex. The PCM communicates with a logic module in the instrument cluster, on a serial bus cable, so it is a binary communication, like a computer uses inside. I will post a link HERE for a schematic of the instrument wiring. Good luck with it, have a great day, and Thanks for using Just Answer.

I hope this helps, 100% satisfaction is my goal. Myself personally, and Just Answer are here to serve you. If the answer is not clear, let me know what additional help you need, and I will assist you further. When you're satisfied, and feel you can leave a positive feedback please accept my answer. I don't get paid unless you do. A bonus and positive feedback are always appreciated, good luck and Thanks.

 

 

 

Customer: replied 2 years ago.
IF I UNDERSTAND WHAT YOU ARE SAYING IS THAT THERE IS ONLY ONE WIRE SENDING THE SIGNAL FOR NUMEROUS THINGS IN THE INSTRUMENT PANEL. THEREFORE, IF ONE WORKS THEN THERE COUNLN'T BE A SHORT. THEN I IMAGING IT IS THE GAUGE THAT IT'S NOT WORKING BUT WHY DOES THE A/C DOESN'T WORK? THEY BOTH FAILED AT THE SAME TIME. THERE IS FREON THE COMPRESSOR IS GOOD AND ALL THE FUSES ARE GOOD. DOES THE PCM TURNS OF THE A/C CLUTCH? THINKING THE CAR IS OVERHEADED OR TOO COLD?
Customer: replied 2 years ago.
I READ THAT THIS IS A COMMON PROBLEM WITH THIS PARTICULAR CAR? WHAT IS NOT COMMON IS THE SOLUTION TO THE PROBLEM?
Expert:  Dr. Hamman replied 2 years ago.

Hi, I am a professional certified mechanic, with an engineering background, and 35+ years experience. I will do my best to assist you.



I have never seen this problem on this model. I will pull up the TSB's (technical Service Bulletins) for this model, and see if it was a recognized problem, I will let you know. If you have any more questions, as always, I am here to help. Good luck with it, have a great day, and Thanks for using Just Answer.

I hope this helps, 100% satisfaction is my goal. Myself personally, and Just Answer are here to serve you. If the answer is not clear, let me know what additional help you need, and I will assist you further. When you're satisfied, and feel you can leave a positive feedback please accept my answer. I don't get paid unless you do. A bonus and positive feedback are always appreciated, good luck and Thanks.





Expert:  Dr. Hamman replied 2 years ago.
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Customer: replied 2 years ago.
THANK YOU
Expert:  Dr. Hamman replied 2 years ago.

Hi, I am a professional certified mechanic, with an engineering background, and 35+ years experience. I will do my best to assist you. At Just Answer the deposit you pay is not payment to the Expert, I only get paid if you click on accept. Also keep in mind I don't know if you are a pro or a novice so we may have to fine tune the answer. Feel free to add any additional info you feel is needed as we go on. Always keep in mind that I am here to help you with any questions.



I spent about an hour digging through TSB's 238 came up, not all were in regard to your model, they were mixed up on the GM database. There was no TSB for the actual problem you have. I believe I would look for a used instrument panel at an auto recycler, or on the internet. That way you will get another logic module, and temp gauge. It might be your best shot ay resolving the problem. If you have any more questions, as always, I am here to help. Good luck with it, have a great day, and Thanks for using Just Answer.

I hope this helps, 100% satisfaction is my goal. Myself personally, and Just Answer are here to serve you. If the answer is not clear, let me know what additional help you need, and I will assist you further. When you're satisfied, and feel you can leave a positive feedback please accept my answer. I don't get paid unless you do. A bonus and positive feedback are always appreciated, good luck and Thanks.




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