Trouble Code E51 Prom Error Indicator

NOTE: To prevent overheating the engine, diagnose this code with engine stopped, ignition on. While in diagnostic mode with engine running and code present, BCM turns off cooling fans and commands air mix door to issue full heat.

If code is a hard failure, it will be displayed continuously until diagnostic mode is exited. If code is an intermittent, it will be displayed in first pass of diagnostic display. Code indicates that calibration PROMs are not being read properly by ECM.

If PROMs are installed backwards or with their pins bent or missing, code may be set. Remove PROM access cover on ECM and verify that PROMs are properly installed.

If PROMs appear to be installed properly, turn ignition off for 10 seconds, and then check if code "E51" remains. If it does remain, replace PROMs. Again turn ignition off for 10 seconds and check for code. If code remains after replacing PROMs, replace ECM.