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Q: Coolant Sensor Code 15 GM on 1990 Chevrolet G Series Van (G20)

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Code-15: Replaced coolant sensor-checked wiring to computer-swapped computer with spare--checked grounds-nothing seems to help--rich starting-pull the plug on coolant sensor and motor will begin to run smoothly--- HELP, This is driving me NUTS!!!! THANKS Dave in Ohio
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It sounds like a wiring problem from your computer to the sensor. I am assuming that you used a new GM Coolant Sensor because there is an updated version of that that comes with a newly designed connector and wiring. See if you can have someone scan the coolant sensor data on your truck to see what the computer is 'seeing' when the sensor is plugged in and when it is unplugged.

here are some shops, they should only charge about 1/2 hour to look at the coolant sensor data
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