shooze Posted May 26, 2019 Share Posted May 26, 2019 Is there only one? My old Nissan Terrano had one for the gauge and one for the ECU. My ECU reads the temperature as 81-85 during normal operation and the fan kicks in at 100. But the gauge sits 2/3 of the way up all the time as in the picture. What would be causing the gauge to read high even though the ECU has it at normal temp? Quote Link to comment Share on other sites More sharing options...
shooze Posted May 28, 2019 Author Share Posted May 28, 2019 Anyone?? Quote Link to comment Share on other sites More sharing options...
karlh Posted May 28, 2019 Share Posted May 28, 2019 In the US it's the same sensor. Quote Link to comment Share on other sites More sharing options...
shooze Posted May 30, 2019 Author Share Posted May 30, 2019 Cheers bud! Any idea why the gauge would read high?? Quote Link to comment Share on other sites More sharing options...
karlh Posted May 30, 2019 Share Posted May 30, 2019 The path from the sensor to the gauge is a bit complicated. The sensor is wired to the ECU. The ECU sends the temperature in a digital word over the CAN bus to the Unified Meter and A/C Amp, the box behind the temperature and fan controls. The Unified Meter and A/C Amp then sends its own signal to the instrument cluster over a dedicated digital bus. The microprocessor in the instrument cluster massages this signal and outputs a voltage to the gauge. Like the fuel gauge, the coolant temperature gauge is damped. Small changes up or down won't show up on the needle. In my 2005 the needle normally reads just below half way. Given the fact that your ECU reading looks good, the problem could be anywhere from the ECU to the gauge. The Service Manual I have for my car says the needle should point in the cold region for temperatures of approximately 50C, in the middle for temperatures between 70C and 105C, and in the hot region for temperatures of approximately 130C. I'm assuming the hot region is the red zone at the top of the gauge, but the manual doesn't define cold or middle. However, the manual does include a signal validity check. The Nissan Consult diagnostic tool can read the temperature provide from the ECU to the Unified Meter and A/C Amp and the temperature from the Unified Meter and A/C Amp to the instrument cluster. If the temperatures agree, the manual says to perform an ECU self-diagnosis, which simply means check for current and pending fault codes. If the temperatures don't agree, the manual says to replace the Unified Meter and A/C Amp. While my manual is for US spec cars, is suspect your car functions in the same manner. Hope this helps. Quote Link to comment Share on other sites More sharing options...
shooze Posted May 30, 2019 Author Share Posted May 30, 2019 1 hour ago, karlh said: The path from the sensor to the gauge is a bit complicated. The sensor is wired to the ECU. The ECU sends the temperature in a digital word over the CAN bus to the Unified Meter and A/C Amp, the box behind the temperature and fan controls. The Unified Meter and A/C Amp then sends its own signal to the instrument cluster over a dedicated digital bus. The microprocessor in the instrument cluster massages this signal and outputs a voltage to the gauge. Like the fuel gauge, the coolant temperature gauge is damped. Small changes up or down won't show up on the needle. In my 2005 the needle normally reads just below half way. Given the fact that your ECU reading looks good, the problem could be anywhere from the ECU to the gauge. The Service Manual I have for my car says the needle should point in the cold region for temperatures of approximately 50C, in the middle for temperatures between 70C and 105C, and in the hot region for temperatures of approximately 130C. I'm assuming the hot region is the red zone at the top of the gauge, but the manual doesn't define cold or middle. However, the manual does include a signal validity check. The Nissan Consult diagnostic tool can read the temperature provide from the ECU to the Unified Meter and A/C Amp and the temperature from the Unified Meter and A/C Amp to the instrument cluster. If the temperatures agree, the manual says to perform an ECU self-diagnosis, which simply means check for current and pending fault codes. If the temperatures don't agree, the manual says to replace the Unified Meter and A/C Amp. While my manual is for US spec cars, is suspect your car functions in the same manner. Hope this helps. Really appreciate you taking the time to reply mate. I shall have a bit of an investigate. I guess its not really an issue I its within than centre section but it would be nice to have it sitting where most others do! At least I know from the ECU its running at a normal temperature. Looks like the Unified Meter/A/C Amp might be what's throwing it out slightly Quote Link to comment Share on other sites More sharing options...
ZMANALEX Posted May 30, 2019 Share Posted May 30, 2019 3 hours ago, karlh said: The path from the sensor to the gauge is a bit complicated. The sensor is wired to the ECU. The ECU sends the temperature in a digital word over the CAN bus to the Unified Meter and A/C Amp, the box behind the temperature and fan controls. The Unified Meter and A/C Amp then sends its own signal to the instrument cluster over a dedicated digital bus. The microprocessor in the instrument cluster massages this signal and outputs a voltage to the gauge. Like the fuel gauge, the coolant temperature gauge is damped. Small changes up or down won't show up on the needle. In my 2005 the needle normally reads just below half way. Given the fact that your ECU reading looks good, the problem could be anywhere from the ECU to the gauge. The Service Manual I have for my car says the needle should point in the cold region for temperatures of approximately 50C, in the middle for temperatures between 70C and 105C, and in the hot region for temperatures of approximately 130C. I'm assuming the hot region is the red zone at the top of the gauge, but the manual doesn't define cold or middle. However, the manual does include a signal validity check. The Nissan Consult diagnostic tool can read the temperature provide from the ECU to the Unified Meter and A/C Amp and the temperature from the Unified Meter and A/C Amp to the instrument cluster. If the temperatures agree, the manual says to perform an ECU self-diagnosis, which simply means check for current and pending fault codes. If the temperatures don't agree, the manual says to replace the Unified Meter and A/C Amp. While my manual is for US spec cars, is suspect your car functions in the same manner. Hope this helps. UK cars operate exactly as USA cars so what you have said is informed and correct. Quote Link to comment Share on other sites More sharing options...
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