Code 51, EGR System & EGR Temp Sensor (EGRTS) Temp Too Low Or High (CALIF. Only)

This code indicates EGRTS has signaled ECM of a temperature greater than, or less than, the calibrated range.

Code 51 will set when the following conditions occur:

• Shorted Sensor.
• Engine coolant temperature is less than 104°F (40°C).
• Exhaust gas temperature is greater than 428°F (220°C).
• Conditions present for 3 seconds. Open Sensor or EGR Valve Passage Plugged.
• Engine coolant temperature is less than or equal to 158°F (70°C).
• Intake air temperature is greater than or equal to 122°F (50°C).
• Conditions present for 80 seconds.

1. Checks if EGR diaphragms are closed at idle. If engine idle roughens when EGR valve is manually opened, passages are not blocked. Temperature will be high if valve is open at idle, or low if passages are blocked.
2. Checks if the EGR valve diaphragms function normally with engine vacuum.
3. Checks if ECM is supplying 5 volts to sensor.
4. Checks if fault is ECM or sensor. Sensor range is approximately 10,000 ohms (hot) to 40,000 ohms (cold). See I - SYS/COMP TESTS article in the ENGINE PERFORMANCE Section.

Fig 1: Code 51 Flow Chart, EGRTS/Temp. Too Low or High (Calif. Only)

Courtesy of GENERAL MOTORS CORP.

Fig 2: Code 51 Schematic, EGRTS/Temp. Too Low or High (Calif. Only)

Courtesy of GENERAL MOTORS CORP.