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check engine light/temp gauge on 0 degrees
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2001 montana
Novice
Apr 1, 2009, 6:58 AM
Post #1 of 10
(3367 views)
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check engine light/temp gauge on 0 degrees
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hello i have a 2001 pontiac montana with a service engine light on & temperature gauge not registering at all 0 degrees, but i have heat & i check fluid levels & checked ok. i have seen leaking (not much) at rear of vehicle on the driver side, it does have a rear heater & cooling controls. any ideas on where to start thank you.
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flgmtech1
User
Apr 1, 2009, 7:23 AM
Post #2 of 10
(3365 views)
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Re: check engine light/temp gauge on 0 degrees
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I am not sure what part of the country you are in, here in Florida the local aftermarket car part stores offer free DTC code reading, this code will help in diagnosing. Generally speaking the issue could be as simple ass a stuck open thermostat but it should still show a relative temp, and or an issue with the ECT sensor or the wiring to the sensor or the Gauge (Part or the IPC) itself. With out a Tech 2 or a scanner with IPC data or engine data to comapre PCM ECT sensor readings it is really hard to say which of these are the cause.
Start with looking at the ECT sensor for issues with connection and or corrosion and if both look goodm, use a multi meter and read resistance of the sensor across the terminals, this will let you know the resistance is either high low or infinite on the sensor.
A
ORN/BLK
469
MAP Sensor Return
B
YEL
410
ECT Sensor Signal
then you need to voltagfe drop test the two wire connector harness side,this will tell you whether or not the circuit is open or if you have high voltage on the signal circuit will induce a Low temperature displal and set a DTC
P0118
The engine coolant temperature (ECT) sensor is a variable resistor, that measures the temperature of the engine coolant. The ECT sensor has a signal circuit and a low reference circuit. The powertrain control module (PCM) supplies 5 volts to the ECT signal circuit and a ground for the ECT low reference circuit. When the ECT is cold, the sensor resistance is high. When the ECT increases, the sensor resistance decreases. With high sensor resistance, the PCM detects a high voltage on the ECT signal circuit. With lower sensor resistance, the PCM detects a lower voltage on the ECT signal circuit. If the PCM detects an excessively high ECT signal voltage, which is a low temperature indication, DTC P0118 sets.
THis would indicate and issue with either the PCM, the ECT sensor or the circuit itself.
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2001 montana
Novice
Apr 1, 2009, 8:20 AM
Post #3 of 10
(3358 views)
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Re: check engine light/temp gauge on 0 degrees
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where do i find more information on these sensors you said to test. i did have the engine light checked & was told the message was check coolant levels & thermostat. but i have heat & pressure on upper hose is good & hot. is one of these sensors on the radiator & called the low coolant sensor.
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flgmtech1
User
Apr 2, 2009, 3:02 AM
Post #4 of 10
(3334 views)
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Re: check engine light/temp gauge on 0 degrees
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you said that you have had the vehicle scanned, what is the code? The sensor I am referring to the ECT or Engine coolant temperature sensor is located on the drivers side at the base of the upper radiator hose thermostat housing in the valley of the intake above the Transmission.
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2001 montana
Novice
Apr 2, 2009, 3:43 AM
Post #5 of 10
(3328 views)
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Re: check engine light/temp gauge on 0 degrees
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I am not sure what the specific code was the only thing i was told was that the computer detected it could not read the temperature or the temperature was out of the range of what the thermostat was rated at & the fluid level should be checked. I will go back today & see if there was a code when the auto parts place plugged into the on board diagnostics test. I changed the coolant sensor you were talking about next to the thermostat housing & temp gauge moves a little bit & just stops. I noticed the 2 main cooling fans seem to be running a lot more than usual, i have been driving it around a little bit.
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flgmtech1
User
Apr 2, 2009, 2:28 PM
Post #6 of 10
(3323 views)
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Re: check engine light/temp gauge on 0 degrees
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if you have replaced the ECT sensor did you happen to use a mulitmeter to test the connector or wiring at the sensor to ensure the problem was not with the wiring? As I said in my earlier post I have a feeling your DTC is related to the ECM seeing high resistance or an issue with the circuit and may only be resolved by repairing the circuit or wire that is affected or if it is internal to the PCM the PCm itself, but first measuring voltage on both circuits and testing for opens, high resistance shorts to voltage or shorts to grounds are absolutely your next step to determine what is causing your concern. For starters you could unplug your map sensor I have included pictures of your engine and the call out for the MAP sensor is number 2.
By unplugging the map sensor then seeing what your temperature gauge is then reading you are taking the low reference side away form the ECT sensor or the ground side, this eliminates any issues with the MAP sensor or wiring to the map sensor on the eniter low reference circuit for both the MAP and the ECT, if you still have no response unlpug the ECT and test the yellow wire for 5 volts this is the signal side and the side that is possibly open or grounded. Use a Digital multi meter and let me know what the measured DC voltage is at the yellow wire terminal of the ECT.
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flgmtech1
User
Apr 2, 2009, 2:31 PM
Post #7 of 10
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Re: check engine light/temp gauge on 0 degrees
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by the way, look for signs of a mouse or a rodent eating at any of your under hood insulation or wiring harness conduit, this may be the cause where by a rodent could have eaten into one of these wires casuing all of these issues.
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2001 montana
Novice
Apr 3, 2009, 7:56 AM
Post #8 of 10
(3301 views)
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Re: check engine light/temp gauge on 0 degrees
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Ok i disconnected the map sensor & measured 5 volts on the grey wire the lite green was no voltage i disconnected the map sensor & ran the car for 20 minutes & saw the gauge move about a 1/4" & stop at the same place everytime. I measured yellow wire & got 5volts at the ect harness. when map sensor was disconnected the car seemed to idle very high about 25,000 rpms
any suggestions Thank you 2001 montana
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flgmtech1
User
Apr 3, 2009, 11:21 AM
Post #9 of 10
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Re: check engine light/temp gauge on 0 degrees
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the vehicle will idle higher as it defaults to a median reading as it does not know if it is above sea level or not. The MAP sensor helps the PCM know what the atmospheric pressure is as read via manifold pressure this determines if atmospheric pressure is say higher elevations in the mountains or flat at or below sea level like some areas here in Florida. I only had you take the MAP sensor connector off to make sure the MAP was not skewing the ECT sensor low reference circuit or the wiring in the circuit, this means if you have been able to read 5 volts at the yellow wire at the ECT sensor and obviously ground at the orange and black wire at the ECT it means the circuit is operating as per designed.
HOWEVER, with out the benefit of a TECH 2 scan tool to see data while the vehicle is running it is hard to determine if the issue is not a IPC issue or an internal PCM issue.
At this stage you really need to obtain a scan tool and see what the live reading is of the ECT to compare with the gauge reading.
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2001 montana
Novice
Apr 5, 2009, 5:15 PM
Post #10 of 10
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Re: check engine light/temp gauge on 0 degrees
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Ok i found the problem out, it was the thermo-stat all along, apparently when the temperature was fluctuating for the last month the service engine light kicked in & shut down the thermostat gauge, also it kicked in the cooling fans, after the sevice engine light was reset the fans immediately shut off & the temp gauge went up to 162 degrees immediately. Also the 25,00 rpms was because i accidently unplugged the throttle sensor & when i plugged it back in the rpms went to normal. So i will start with replacing the thermo-stat & go from there.
Thank you for your input 2001 montana
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