DTC 71

DTC 71 Diagnostic Chart - Part 1 0f 2:

DTC 71 Diagnostic Chart - Part 2 Of 2:

EGR System:

Circuit Description:
The exhaust gas recirculation (EGR) temperature sensor is a thermistor (a variable resistor that changes along with EGR temperature changes) in series with a fixed resistor within the powertrain control module (PCM). The PCM applies 5 volts to the sensor. The PCM monitors the voltage across the EGR temperature sensor and coverts it into a temperature reading. When the exhaust gases are cold the sensor resistance is high, and when the exhaust gases are warm the sensor resistance is low. Therefore, when the exhaust gases are cold the PCM will receive a high voltage input, and when the exhaust gases are warm the PCM will receive a low voltage input. The PCM also maintains control over a EGR solenoid vacuum (SV) valve. The EGR SV valve permits exhaust EGR to be recirculated and incorporated into the combustion process. The PCM will determine the best time to energize the EGR SV valve by monitoring the EGR exhaust gas temperature.

DTC 71 will set if the following condition is met:

^ With ECT above 60° C (140° F) with EGR temperature less than 70° (158° F) for at least 50 seconds.

Test Description:
Numbers below refer to circled numbers on the diagnostic chart.

1. This checks the power feed to the sensor.

2. This checks the ground circuit to the sensor.

3. This checks the EGR temperature resistance vs.EGR temperature values.

4. This checks the power feed circuit to the EGR SV valve.

5. This checks for a faulty EGR SV valve mechanical checks and for a faulty PCM.

Diagnostic Aids:
Check EGR vacuum modulator and EGR valve for sticking open or closed.

An intermittent may be caused by a poor connection, rubbed through wire insulation, or a wire broken inside the insulation. Inspect hamess connectors for backed out terminals, improper mating, broken locks, improperly formed or damaged terminals and poor terminal-to-wire connections before component replacement.