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Discussion Starter · #1 ·
Hi I have a Peugeot 3008 petrol vti with an electrical fault I’m trying to solve .I’ve used Diagbox to clear faults but 2 remain ‘7155 temp data fault’ in the bsi section & ‘P0118 Engine Coolant Temperature (ECT) sensor circuit high open’ .When I start the car after 5/10 seconds the rad fan starts, Engine fault repair needed is shown, followed shortly after temp gauge goes to max then Engine temp fault stop the vehicle .I’ve changed the temp (green)sensor and checked feed wire voltage 5v but no change ,fan continues when engine is turned off ,on the thermostat there is a built in second sensor but I can’t find out what its function is ,could this be the cause of the problem does anyone have any idea
 

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A lot of Peugeots have a piloted thermostat. This means there is a small heating element in the thermostat to vary when it opens. The second connection on the thermostat which looks a bit like a sensor is the connection to the heater.

The temperature sensor is a thermistor. Normally at 25C they have usually have a resistance of 5,000 Ohms and this resistance reduces as the temperature increases. If you are measuring 5V it suggest the sensor is open circuit. Perhaps the plug is not making a proper contact with the sensor. Can you set your meter to Ohms and measure the resistance between the sensors two pins?
 

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Also did you clear codes in the BSI. I found on some VTI engine BSI fault code for coolant sensors does not auto clear when you change the sensor.

This causes the stop light, full temp on the gauge and constant fan until you clear the BSI code with a reader

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Discussion Starter · #5 ·
Also did you clear codes in the BSI. I found on some VTI engine BSI fault code for coolant sensors does not auto clear when you change the sensor.

This causes the stop light, full temp on the gauge and constant fan until you clear the BSI code with a reader

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I've tried numerous times to clear fault code but p0118 won't clear
 

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Is that with planet/diagbox etc or a standard code reader as you need one that will do body system not just engine

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With diagbox
If you are measuring 5V at the sensor when it's connected it suggest to me there is still a fault associated with the sensor. The normal way to monitor thermistors is to make them part of a voltage divider. Basically when the thermistor is disconnected there should be 5V between the plugs two pins and when the thermistor is connected this voltage should drop. Your car may use a different reference voltage but 5V is normal.
 

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Discussion Starter · #9 ·
Sensor is ok and wiring is intact, but I don't seem to be getting a ground feed from the Ecu, if I supply a ground from the engine to the wire temp gauge works fine but the cooling fan still comes on from cold and stays on so may this is causing the issue or possibly the Ecu
 

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When you got the gauge working did you try clearing the fault with diagbox?

When you measured 5V was it with the sensor unplugged? If you were able to access the back of the plug with the meter probes when the connector was connected I doubt you would have measured 5V if there was a poor earth. The diagram below shows a typical voltage divider. If the negative supply to the thermistor had a poor connection (e.g. at the ECU end) you could still read 5V if the thermistor was unplugged.


Rectangle Parallel Font Circuit component Electric blue
 

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Discussion Starter · #11 ·
Jumping the ground (black) wire it allowed me to clear all faults, started the engine again was ok for a short time got to about 70 degrees and on came the fan I don’t think the temp reading was accurate. The 5v reading was gained by using a needle probe on the feed wire back of sensor and ground to engine as if using the black wire for ground was getting 0.05v, also sensor disconnected and probing the plug same reading .shorting the sensor plug the -40 temp reading did not change on the live feed. As I obtained this car with this fault it seems someone has fitted a new green sensor to try a fix but I’m now wondering if I have the correct one as a lot of parts lists give an option of the longer brown sensor
 

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Have you looked at the large brown plug ( 53V MR) on the ECU? I suspect it may have got some water in it. The sensor connects to Pin 14 and 32 of that connector. I don't have pin location details but I expect 14 and 32 are near each other.
 

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Discussion Starter · #17 · (Edited)
Have you looked at the large brown plug ( 53V MR) on the ECU? I suspect it may have got some water in it. The sensor connects to Pin 14 and 32 of that connector. I don't have pin location details but I expect 14 and 32 are near each other.
It's dry with no sign of any water contamination ,I did wrap a fine wire around 14 ground pin of the ecu and put the plug back in and jump that to the sensor but still no ground connection when putting a meter across the sensor plug ,going to check the main ground wires to the ecu to see if there is any problem with the feed Rectangle Font Parallel Pattern Number
 

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It's dry with no sign of any water contamination ,I did wrap a fine wire around 14 ground pin of the ecu and put the plug back in and jump that to the sensor but still no ground connection when putting a meter across the sensor plug ,going to check the main ground wires to the ecu to see if there is any problem with the feed
I understand what you are trying but the black wire may not be a direct earth. There may be a resistor to earth (bias resistor) as shown below. I think it would be worth checking for a partial short between the two wires. Unplug both ends and check if there is a low resistance -e.g 50 Ohms.

Font Parallel Computer networking Rectangle Diagram
 

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Gauge same as with it connected to full temp
The sensor has a negative coefficient of resistance so if the sensor is unplugged the gauge should read a very cold temperature. If the sensor has a partial short circuit in its connection is will read a very high temperature. My guess there is a partial short circuit in the cable between the sensor and ECU.

There is one caveat on the above and that is - the BSI controls the temperature gauge so it may be programmed to show a high temperature if the probe is disconnected.
 

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Discussion Starter · #20 ·
I understand what you are trying but the black wire may not be a direct earth. There may be a resistor to earth (bias resistor) as shown below. I think it would be worth checking for a partial short between the two wires. Unplug both ends and check if there is a low resistance -e.g 50 Ohms.

View attachment 96380
ok I've checked both wires and get 1.4 & 1.3 Ohms ,also ch
ecked with everything connected with ignition on and getting 5v on the black wire which apparently its supposed to read 0 to .02v so possibly an ecu fault
Product Communication Device Output device Font Portable communications device
 
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