[drx4mc]

Hey guys I'm having this issue recently that I cannot resolve. I'm getting a check engine light for P15e8 which is a faulty engine coolant temperature sensor.
I've bled both the high and low pressure coolant pumps over 10x according to the ISTA+ procedure guidelines, the fault code resolves for two days then comes back on after 30ish miles of driving.

I haven't tested the sensor yet because I assumed this was due to air in the coolant lines after installing upgraded stage 2 turbos. I recently purchased this car several days ago and I'm unsure if this was an issue prior to purchase.

The coolant system was pressure tested and showed no coolant leaks.

-Apart from this I'm getting a rough idle and poor gas mileage around 7-8mpg which seems odd given that was the average mileage I got from my F90 M5 with 800rwhp after typical city stop and go driving.

-The cars internal temperature sensor is also inaccurate, it starts out at 120F on a hot day and gradually decreases from there until about 10-15 degrees above what the outside temperature actually is.

-The AC and heat both are functioning perfectly fine when not set on automatic.

-I'm not sure what is and isn't related to the current check engine light issue, these are what I have observed from recent driving. Was wondering if anyone recently came across this issue as well or if anyone has any insight I would greatly appreciate any help.

[joebie3]

Originally Posted by drx4mc

Hey guys I'm having this issue recently that I cannot resolve. I'm getting a check engine light for P15e8 which is a faulty engine coolant temperature sensor.
I've bled both the high and low pressure coolant pumps over 10x according to the ISTA+ procedure guidelines, the fault code resolves for two days then comes back on after 30ish miles of driving.

I haven't tested the sensor yet because I assumed this was due to air in the coolant lines after installing upgraded stage 2 turbos. I recently purchased this car several days ago and I'm unsure if this was an issue prior to purchase.

The coolant system was pressure tested and showed no coolant leaks.

-Apart from this I'm getting a rough idle and poor gas mileage around 7-8mpg which seems odd given that was the average mileage I got from my F90 M5 with 800rwhp after typical city stop and go driving.

-The cars internal temperature sensor is also inaccurate, it starts out at 120F on a hot day and gradually decreases from there until about 10-15 degrees above what the outside temperature actually is.

-The AC and heat both are functioning perfectly fine when not set on automatic.

-I'm not sure what is and isn't related to the current check engine light issue, these are what I have observed from recent driving. Was wondering if anyone recently came across this issue as well or if anyone has any insight I would greatly appreciate any help.

My first order of business would be to either test, or replace, the coolant temp sensor. That could have effect on some of the issues you're seeing. Have you read out what the sensor is actually reading for temp?

[drx4mc]

Originally Posted by joebie3

My first order of business would be to either test, or replace, the coolant temp sensor. That could have effect on some of the issues you're seeing. Have you read out what the sensor is actually reading for temp?

Thanks for getting back to me, will place an order for one today.

I was monitoring the temperatures today while city driving, I was getting 103C from cold start to a high of about 106C.

Checked on the forums and I'm seeing that this falls within normal range?

[joebie3]

Can you run any diagnostics on that sensor through ISTA when you run a scan? I haven't explored that side of the program yet.

[Potatohead-M2]

Originally Posted by drx4mc

Thanks for getting back to me, will place an order for one today.

I was monitoring the temperatures today while city driving, I was getting 103C from cold start to a high of about 106C.

Checked on the forums and I'm seeing that this falls within normal range?

103C would not be normal for a cold start, that is normal operating temp once warm.

[drx4mc]

I was fiddling with the hidden menu, trying to gain access which took awhile. I tried again now that Im better versed in accessing the menu and I'm reading 96C on a cold start, which also does not sound normal, as the oil temperature was reading close to the outside atmospheric temperature (76F).

[Potatohead-M2]

Originally Posted by drx4mc

I was fiddling with the hidden menu, trying to gain access which took awhile. I tried again now that Im better versed in accessing the menu and I'm reading 96C on a cold start, which also does not sound normal, as the oil temperature was reading close to the outside atmospheric temperature (76F).

If the vehicle has been sitting a while the coolant and oil temps will be close to ambient. ~100C is way, way too hot, for this planet anyway.

[drx4mc]

Originally Posted by joebie3

Can you run any diagnostics on that sensor through ISTA when you run a scan? I haven't explored that side of the program yet.

Unfortunately I wasn't able to find any more specific information for this sensor through ISTA+, thats probably due to my lack of knowledge.

Originally Posted by Potatohead-M2

If the vehicle has been sitting a while the coolant and oil temps will be close to ambient. ~100C is way, way too hot, for this planet anyway.

Finally was able to check this morning after having it sit overnight for 12hrs. Its reading 29C or 84F when ambient air is 51F.
I'll going to try replacing the sensor today and will keep you guys posted.

[joebie3]

Originally Posted by drx4mc

Unfortunately I wasn't able to find any more specific information for this sensor through ISTA+, thats probably due to my lack of knowledge.



Finally was able to check this morning after having it sit overnight for 12hrs. Its reading 29C or 84F when ambient air is 51F.
I'll going to try replacing the sensor today and will keep you guys posted.

I was looking too, but I wasn't connected to the car, I didn't see anything jump out at me. Might have some time to look today.

[drx4mc]

Originally Posted by joebie3

I was looking too, but I wasn't connected to the car, I didn't see anything jump out at me. Might have some time to look today.

Originally Posted by Potatohead-M2

If the vehicle has been sitting a while the coolant and oil temps will be close to ambient. ~100C is way, way too hot, for this planet anyway.

Strange turn of events, seems like a much bigger issue than I had thought originally. I did several hard resets through ISTA+ and Autel through a friend of mine. I managed to get the temperature sensor code and check engine light removed however they are both showing a Kombi Terminal 30 error which is for the instrument cluster.
Date and Time are not saved as well as trip mileage. I replaced and had a new battery reprogrammed as the previous battery was showing low health and this did not resolve the date/time issue.
I will leave the negative battery terminal removed for several hours to possibly reset the electrical components, then retest and report back.

[drx4mc]

We finally solved this issue, I wanted to give everyone an update to help someone else if they come across the same problem.

There ended up being a short behind the instrument cluster. An oem wire covering had come loose over time causing the wire to short whenever contact was being made.

This ended up causing the instrument cluster and several other fuses to blow.

Some issues I was experiencing was Kombi Terminal 30 error with lack of power and IHKA Terminal 30 lack of power along with a faulty temperature sensor and later an engine overheating warning.

[cutnsew]

electrical gremlin. What a PITA. Thanks for posting a follow up, and glad you got it fixed!

[joebie3]

Originally Posted by drx4mc

We finally solved this issue, I wanted to give everyone an update to help someone else if they come across the same problem.

There ended up being a short behind the instrument cluster. An oem wire covering had come loose over time causing the wire to short whenever contact was being made.

This ended up causing the instrument cluster and several other fuses to blow.

Some issues I was experiencing was Kombi Terminal 30 error with lack of power and IHKA Terminal 30 lack of power along with a faulty temperature sensor and later an engine overheating warning.

Nice!! Glad you got it figured out, what a random issue.