Electrics: - False high engine temperature warning

trimjim · Jan 16th, 2020, 17:11

03 V70
I had a false high engine temperature warning. Had garage look and they fitted new sensor which cured problem for several months. However the warning is back now. Disconnecting the battery for a few minutes removed the warning, so I assumed the problem was in the 'computer' not the sensor. That worked fine for a while but the warning now keeps returning. Disconnecting the battery clears it still, but it comes back after a few days. Any thoughts, please?
Trimjim.

oragex · Jan 16th, 2020, 20:02

By warning, did you got a display message, or rather the coolant temperature climbed into the hot zone ?

trimjim · Jan 17th, 2020, 16:59

Quote:

Originally Posted by trimjim

03 V70
I had a false high engine temperature warning. Had garage look and they fitted new sensor which cured problem for several months. However the warning is back now. Disconnecting the battery for a few minutes removed the warning, so I assumed the problem was in the 'computer' not the sensor. That worked fine for a while but the warning now keeps returning. Disconnecting the battery clears it still, but it comes back after a few days. Any thoughts, please?
Trimjim.

Thanks - the warning 'high engine temperature - stop safely'. shows and the temp. gauge shows max temp. but the actual engine temp. is quite normal. the warning displays as soon as the car is started.

oragex · Jan 17th, 2020, 23:22

Inexpensive sensor can have a problem, but I would look first closer to the two wires going inside the electrical connector at the sensor - these can break or make a short at this place

yohanvolvo · Oct 26th, 2022, 23:40

It appears that driving with the MAF sensor electrical plug disconnected results in a false "High Engine Temperature" warning in 2007 S40. Here is what happened and what I had to do to reset.

I removed and cleaned the MAF of a 2007 S40 to hopefully clear CEL P0171. After I reinstalled MAF, I failed to insert the MAF electrical connector. I drove several round trips without any noticeable issues other than the CEL light, which I did not reset after cleaning MAF.

On the 5th trip "High Engine Temperature" warning appeared. The engine wasn't so hot and I assumed it was the engine temperature sensor. Purchased a new sensor and plugged it in with the sensor outside but grounded. The same false "High Engine Temperature" warning persisted. So, I concluded that the temperature sensor was unlikely to be faulty

I plugged MAF electrical connector plug and reset the CEL codes. Yet the "High Engine Temperature" warning continued to stay for the next 3 days while CEL did not come back on. I disconnected the battery and waited 30 mins. Now the false "High Engine Temperature" warning appears to have gone.
If anyone knows how the MAF and Engine Temperature readings are connected in S40, I'd love to hear.

Jan 16th, 2020, 17:11	#1
trimjim New Member Last Online: Feb 24th, 2021 13:08 Join Date: Mar 2018 Location: Truro	False high engine temperature warning 03 V70 I had a false high engine temperature warning. Had garage look and they fitted new sensor which cured problem for several months. However the warning is back now. Disconnecting the battery for a few minutes removed the warning, so I assumed the problem was in the 'computer' not the sensor. That worked fine for a while but the warning now keeps returning. Disconnecting the battery clears it still, but it comes back after a few days. Any thoughts, please? Trimjim.

Jan 16th, 2020, 20:02	#2
oragex Premier Member Last Online: Jul 26th, 2021 21:24 Join Date: Jun 2013 Location: Coldnada	By warning, did you got a display message, or rather the coolant temperature climbed into the hot zone ? __________________ Several Volvo Repair Videos https://www.youtube.com/playlist?lis...ECTts0FSVSOT_c

Jan 17th, 2020, 23:22	#4
oragex Premier Member Last Online: Jul 26th, 2021 21:24 Join Date: Jun 2013 Location: Coldnada	Inexpensive sensor can have a problem, but I would look first closer to the two wires going inside the electrical connector at the sensor - these can break or make a short at this place __________________ Several Volvo Repair Videos https://www.youtube.com/playlist?lis...ECTts0FSVSOT_c

Oct 26th, 2022, 23:40	#5
yohanvolvo New Member Last Online: Jun 27th, 2023 17:41 Join Date: Mar 2012 Location: Ashburn	False high engine temperature warning - MAF unplugged It appears that driving with the MAF sensor electrical plug disconnected results in a false "High Engine Temperature" warning in 2007 S40. Here is what happened and what I had to do to reset. I removed and cleaned the MAF of a 2007 S40 to hopefully clear CEL P0171. After I reinstalled MAF, I failed to insert the MAF electrical connector. I drove several round trips without any noticeable issues other than the CEL light, which I did not reset after cleaning MAF. On the 5th trip "High Engine Temperature" warning appeared. The engine wasn't so hot and I assumed it was the engine temperature sensor. Purchased a new sensor and plugged it in with the sensor outside but grounded. The same false "High Engine Temperature" warning persisted. So, I concluded that the temperature sensor was unlikely to be faulty I plugged MAF electrical connector plug and reset the CEL codes. Yet the "High Engine Temperature" warning continued to stay for the next 3 days while CEL did not come back on. I disconnected the battery and waited 30 mins. Now the false "High Engine Temperature" warning appears to have gone. If anyone knows how the MAF and Engine Temperature readings are connected in S40, I'd love to hear.

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