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Vauxhall Vectra 1.8 code P0115 Coolant temp sensor circuit fault

Posted By Leighdp 6/24/2008 5:02:51 PM
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Vauxhall Vectra 1.8 code P0115 Coolant temp sensor circuit fault

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Leighdp
 Posted 6/24/2008 5:02:51 PM
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Last Active: 10/25/2008 10:53:10 AM
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Hi Everyone,

I have been looking at this car today for a colleague. Just recently the temp gauge has been acting slightly weird and just jumping from cold to 90. Then on Sunday night the MIL came on. He had it towed to our work and I scanned it and found the code above.

I have done some basic checks on the temp sensor, i.e resistance checks and voltage across the 2 wires going into it. It all seems to be normal. I have also cleaned up the terminals and made sure the plug was fitted securely. I then erased the code and all was well for a while. Then after a couple of short journeys the MIL came back on when he had just parked it up. I wasn't able to test the sensor at that point as I wasn't with the car at the time. So I then did another scan today, and found the same fault code. I cleared the code and ran the car trying to get the MIL to come back on again so I could test the sensor to see if that is causing the light to come on, but the light stayed out.

Has anyone come across this before and if so what is the remedy for it? Also, am I missing something in my test results as I think they look pretty normal. I don't have live data for it as my diagnostic kit isn't that thorough I'm afraid.

Test results:

Sensor resistance 21c - 3400 ohms

Sensor resistance 76c - 230 ohms

voltage across sensor 21c - 3.7v

voltage across sensor 76c - 2.3v.

My next test which I will do is to test the wiring from the ECM but thought I would ask for some advice over what I have done already.

Thanks in advance as always for any advice given.

Lee

topbloke
 Posted 6/25/2008 2:49:56 AM
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if this is an x18xe1 engine there is a modified cable and plug and sensor with gold contacts which causes this code however you say its an x18xe the temp sensor that you are checking is not related to the gauge on the dash seperate sensor, one wire, if it is the xe1 engine they are not unknown to loose the earths on airflow sensor and temp sensor as they share the same earth
Leighdp
 Posted 6/25/2008 5:21:38 AM
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Hi Topbloke,

I had thought that was the case. I cleaned up the single wired sensor and the gauge now seems to be working normally. As for the engine code it is definately the X18XE. The owner has owned this car from new and he still has all the original documents that came with the car.

I think the sensor is going open circuit when it reaches the higher temperature and causing the EML to come on. I'm just having trouble proving it without live data. The only option I think is to send this one to someone with better diagnostics equipment.

Cheers

Lee

topbloke
 Posted 6/25/2008 1:10:42 PM
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Last Active: 10/9/2012 5:02:22 PM
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okay, normally if the temp sensor mucks about it tends to go open circuit and defalts to a rich mixture causing stalling rough running etc but they are cheap enough to buy and replace about £12 iirc  

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