Bad coolant temp sensor or ground? Help asap
06-18-2009, 02:53 PM
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Bad coolant temp sensor or ground? Help asap My 99 trans am has been having trouble starting lately and finally threw p0118. It has a High Voltage reading from the coolant temp sensor. I did some searching and found that the sensor might be fine but it may just be a bad ground? When the car starts acting up the temp gauge goes to 0 but most times it is fine. What makes it randomly do this? I just bought a new sensor but Im not going to replace it unless Im sure it is. Thanks
EDIT: The car once again barely starts and then it it finally starts the idle goes up to 1300 and temp sensor is all the way down and the fans kick on. Any other ides guys I'm pissed.
EDIT: The car once again barely starts and then it it finally starts the idle goes up to 1300 and temp sensor is all the way down and the fans kick on. Any other ides guys I'm pissed.
Last edited by fbodyman1026; 06-23-2009 at 02:24 PM.
06-18-2009, 03:41 PM
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alright I swapped it out for a new one and it the temp came up for a second then it went right back to zero and the fans kicked on for some reason. What do I look for now?
06-18-2009, 10:10 PM
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Not sure if sensors share the same ground as the coil packs (since I believe theyre in the same wireloom) but I know the coil pack grounds are on the back of the head, one wire for one side of the motor another wire for the other.
06-19-2009, 08:00 AM
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ok, do you happen to have access to HP tuners or a Tech 2?
THe reason I ask is, that its possible that the gauge in the cluster is defective. I'm curious what the PCM is seeing for a temp. but if no access, try..
Terminal 'A' is sensor ground, and 'B' is sensor signal to PCM, unplug the sensor and see if you are getting a ground signal. a logic probe works best for this.
THe reason I ask is, that its possible that the gauge in the cluster is defective. I'm curious what the PCM is seeing for a temp. but if no access, try..
Terminal 'A' is sensor ground, and 'B' is sensor signal to PCM, unplug the sensor and see if you are getting a ground signal. a logic probe works best for this.
06-19-2009, 03:07 PM
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ok, do you happen to have access to HP tuners or a Tech 2?
THe reason I ask is, that its possible that the gauge in the cluster is defective. I'm curious what the PCM is seeing for a temp. but if no access, try..
Terminal 'A' is sensor ground, and 'B' is sensor signal to PCM, unplug the sensor and see if you are getting a ground signal. a logic probe works best for this.
THe reason I ask is, that its possible that the gauge in the cluster is defective. I'm curious what the PCM is seeing for a temp. but if no access, try..
Terminal 'A' is sensor ground, and 'B' is sensor signal to PCM, unplug the sensor and see if you are getting a ground signal. a logic probe works best for this.
Is terminal A towards the front drivers side in the engine bay? If so I think the problem is solved.
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07-07-2009, 08:52 PM
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i know this is kinda old but may help someone elese
i bought a coolent sensor from autozone and it gave me to same code stupid part was 20$ with tax
i went to orileys and got one diff brand and only 11$
Bottom line the cheaper one worked first try no codes nothing now which makes me think the duralast sensor does not work not sure tho but maby help someone
i bought a coolent sensor from autozone and it gave me to same code stupid part was 20$ with tax
i went to orileys and got one diff brand and only 11$
Bottom line the cheaper one worked first try no codes nothing now which makes me think the duralast sensor does not work not sure tho but maby help someone
07-07-2009, 09:06 PM
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Have you checked the connector/wires? My idle would drop and then catch itself, I thought it was just the tunning for the cam but one day while messing with the engine I bumped the wire loom that the coolant temp sensor goes in and the idle dropped and caught itself. I replaced the connector/wire (I think it is Delco#PT1798) Maybe this will help.
08-24-2016, 12:58 PM
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Have you checked the connector/wires? My idle would drop and then catch itself, I thought it was just the tunning for the cam but one day while messing with the engine I bumped the wire loom that the coolant temp sensor goes in and the idle dropped and caught itself. I replaced the connector/wire (I think it is Delco#PT1798) Maybe this will help.
When I drive when the problem occurs I feel like a hesitation then a tug and then sounds like the car is sucking in air like a vaccum... After reverting the codes drive it around the block a couple time now the only thing left is the temp gauge rpm sensor and fans staying on
03-19-2018, 09:57 PM
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Bringing up an old topic if anyone can chime in. My car started doing this! Bought a new sensor $35 bucks and still same issue. The 3 wires going into the sensor were exposed so I tried to tape them up. Is it more likely a short/ground vs a bad sensor? 1998 Z28 stock
03-19-2018, 10:40 PM
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This really seems to be a simple ground issue. I'd check the wires for continuity at either end. When you throw a temp sensor to ground, it will read the lowest possible reading. This also occurs if signal is lost. Either way, these sound like old wires cracking and shorting out somewhere.
Look at the bright side though, you can clean up your engine bay while your digging through the harness checking stuff out. I'd open up that old crappy loom and chase the wires down, all the way to the pcm. It's not hard, just tedious. Re wrap everything back up with a quality loom and tuck as needed, once you figure out the problem.
I do this on purpose to my IAT sensor, to force the engine to pull a specified amount of timing when I flip the switch. It grounds the sensor out and makes it go to the lowest setting.
Look at the bright side though, you can clean up your engine bay while your digging through the harness checking stuff out. I'd open up that old crappy loom and chase the wires down, all the way to the pcm. It's not hard, just tedious. Re wrap everything back up with a quality loom and tuck as needed, once you figure out the problem.
I do this on purpose to my IAT sensor, to force the engine to pull a specified amount of timing when I flip the switch. It grounds the sensor out and makes it go to the lowest setting.
03-19-2018, 10:50 PM
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The wires going to the sensor and water pump have already been re-wrapped. Wondering if because there was exposed copper on all 3 wires by the pigtail if that’s where it’s shorting. Coil packs have new ground
