Code 51, EGR System & Exhaust Gas Recirculated Temperature EGRTS) (Ca Only) Temperature Too Low Or Too High

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

1. This 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 blocked.
2. This checks if EGR valve diaphragms will function normally with engine vacuum.
3. This checks if ECM is supplying 5 volts to sensor.
4. This checks if fault is ECM or sensor. Sensor range is 400,000 ohms cold to approximately 10,000 ohms hot.

Fig 1: Code 51, Circuit Wiring Diagram & Flow Chart

Courtesy of GENERAL MOTORS CORP.