Code 51 - Mid Temperature Switch
- Ensure that coolant temperature was above 128°F (53°C) during "Functional Test" when code was observed.
- Check contacts of mid temperature switch (should be closed above 128°F/53°C). If resistance measures less than 5 ohms, go to step 3). If above 5 ohms, replace mid temperature switch.
- Measure resistance in wiring between MCU (pins 5 & 14) and mid temperature switch. If resistance is less than 5 ohms, replace MCU module. If greater than 5 ohms, repair wiring.
- Disconnect harness from mid temperature switch and measure resistance between wire leading to MCU pin 5 and ground. If resistance is less than 1000 ohms, repair wire leading to MCU pin 5. If resistance is greater than 1000 ohms, replace MCU.