COOLANT level low
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Joined: Oct 2022
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COOLANT level low
1st off, I read alot of post on here already.
I was driving few nights ago with no issues. Next morning i went to start the car, and it turned over fast but rough and had hard time starting. Drove 10 mins and saw the infamous...low coolant level. It bounced around 15 mins before going into limp mode. Shut down, coolant full, not overheating. Started up, gauge was bouncing 175 to 203. Drove 30 mins home without issue other than car running rough when the bouncing started again.
Replaced temp sensor, i believe all air is purged, fluid level full but has not gone down, no leaks. I pulled battery leads for abit. Still getting the same condition, but its not constant, it is spiratic
I was driving few nights ago with no issues. Next morning i went to start the car, and it turned over fast but rough and had hard time starting. Drove 10 mins and saw the infamous...low coolant level. It bounced around 15 mins before going into limp mode. Shut down, coolant full, not overheating. Started up, gauge was bouncing 175 to 203. Drove 30 mins home without issue other than car running rough when the bouncing started again.
Replaced temp sensor, i believe all air is purged, fluid level full but has not gone down, no leaks. I pulled battery leads for abit. Still getting the same condition, but its not constant, it is spiratic
Burning Brakes
Joined: Jun 2022
Posts: 750
Likes: 255
From: Florida
1st off, I read alot of post on here already.
I was driving few nights ago with no issues. Next morning i went to start the car, and it turned over fast but rough and had hard time starting. Drove 10 mins and saw the infamous...low coolant level. It bounced around 15 mins before going into limp mode. Shut down, coolant full, not overheating. Started up, gauge was bouncing 175 to 203. Drove 30 mins home without issue other than car running rough when the bouncing started again.
Replaced temp sensor, i believe all air is purged, fluid level full but has not gone down, no leaks. I pulled battery leads for abit. Still getting the same condition, but its not constant, it is spiratic
I was driving few nights ago with no issues. Next morning i went to start the car, and it turned over fast but rough and had hard time starting. Drove 10 mins and saw the infamous...low coolant level. It bounced around 15 mins before going into limp mode. Shut down, coolant full, not overheating. Started up, gauge was bouncing 175 to 203. Drove 30 mins home without issue other than car running rough when the bouncing started again.
Replaced temp sensor, i believe all air is purged, fluid level full but has not gone down, no leaks. I pulled battery leads for abit. Still getting the same condition, but its not constant, it is spiratic
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Joined: Sep 2013
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From: Cape Coral, Florida
Since there is no real coolant level sensor the ECM looks at ECT vs. RPM so maybe you need a new ECT sensor to fix this...if the ECM "thinks" the engine is overheating it will start shutting off injectors...your rough running condition....to see what ECT the ECM is seeing you need a scan tool that can look at Global OBD2 data...not on the enhanced or factory side.
Last edited by C5 Diag; Jul 5, 2023 at 11:09 AM.
Thread Starter
Instructor
Joined: Oct 2022
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Since there is no real coolant level sensor the ECM looks at ECT vs. RPM so maybe you need a new ECT sensor to fix this...if the ECM "thinks" the engine is overheating it will start shutting off injectors...your rough running condition....to see what ECT the ECM is seeing you need a scan tool that can look at Global OBD2 data...not on the enhanced or factory side.
Moderator, Tech Contributor
Joined: Sep 2013
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From: Cape Coral, Florida
Yea, im thinking ecm, everytime it seems fixed, a new sensor throws a code. I replace that, clear computer, and the temp sensor issue returns. So far i have new ect, maf, map, new ect connector and wire back to ecm, new tstat, new antifreeze, checked 4 ground points and changed the ends on several. Its getting ridiculous.
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did thermostat as well. Does GM do the update? I bet they charge a fortune
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on the laptop, the ect was bouncing both with car not running or running. Usually 20 to 30* bounces, and 212* is a common number when it acts up. Ocassional 253* spike happens too
Moderator, Tech Contributor
Joined: Sep 2013
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From: Cape Coral, Florida
Since it’s bouncing around like that even with the engine not running (do you mean engine OFF ignition ON ??) to I’d disconnect the ECT sensor and with the ignition ON you will see a 5 volt reference on that yellow wire…you’ll need to actually shake the wiring from the sensor to the ECM as much as you can and see if that 5 volts jumps around…I would check the reference ground also…disconnect the C2 ECM connector and look there to…the yellow and tan wires are pins 21 and 21…there may be some pin fitment issues at the ECM.
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Since it’s bouncing around like that even with the engine not running (do you mean engine OFF ignition ON ??) to I’d disconnect the ECT sensor and with the ignition ON you will see a 5 volt reference on that yellow wire…you’ll need to actually shake the wiring from the sensor to the ECM as much as you can and see if that 5 volts jumps around…I would check the reference ground also…disconnect the C2 ECM connector and look there to…the yellow and tan wires are pins 21 and 21…there may be some pin fitment issues at the ECM.
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Joined: Sep 2013
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From: Cape Coral, Florida
I don't know where you are located but look around for shops that do programming. It DOESN'T have to be a dealership....what you can try is to give the reference ground wire another ground say at battery negative...back probe the reference ground wire and run a wire from the ECT sensor to battery negative...the reference ground is a discrete ground which there are many at the ECM and the ECM has a ground wire on the block...see what happens.
Last edited by C5 Diag; Jul 5, 2023 at 01:41 PM.
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Joined: Sep 2013
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From: Cape Coral, Florida
pulling the connector does a -40 on the laptop. I replaced the ect connector and wiring to the ecm..2 inches from the connector at the ecm. The sensor readings bounce with car off, ignition on, and sensor sitting still. Im looking at the ECM as the issue i guess. Or an update
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