DTC 71

DTC 71 EGR System Malfunction






CIRCUIT DESCRIPTION



The EGR system recirculates exhaust gas, which is controlled to the proper quantity to suit the driving conditions, into the intake air mixture to slow down combustion, reduce the combustion temperature and reduces NOx emissions. The amount of EGR is regulated by the EGR vacuum modulator according to the engine load.

If even one of the following conditions is fulfilled, the VSV is turned OFF by a signal from the ECM. This results in atmospheric air acting on the EGR valve, closing the EGR valve and shutting off the exhaust gas (EGR cut-off).
Under the following conditions, EGR is cut to maintain driveability.
- Engine coolant temp. below 53°C (127°F).
- During deceleration (throttle valve closed).
- Light engine load (amount of intake air very small).
- Engine speed over 4,400 rpm.
- Engine racing.


WIRING DIAGRAM





DIAGNOSTIC TROUBLE CODE DETECTION DRIVING PATTERN

Purpose of the driving pattern:
- To simulate diagnostic trouble code detecting condition after diagnostic trouble code is recorded.
- To check that the malfunction is corrected when the repair is completed confirming that diagnostic trouble code is no longer detected.

Malfunction: Open in EGR gas temp. sensor circuit

NOTE: If the conditions in this test are not strictly followed, detection of the malfunction will not be possible.





1. Disconnect the "EFI" fuse (15 A) for 1O seconds or more, with the ignition switched OFF. Initiate test mode (Connect terminals TE2 and E1 of the data link connector, (DLC1) with the ignition switched OFF).
2. Start the engine and warm it up.
3. Let the engine idle for 3 minutes.
4. With the A/C ON and transmission in 5th gear (or "D" position for A/T), drive at 88 - 96 km/h (55 - 60 mph) for 4 minutes or less.
- If a malfunction exists, the Malfunction Indicator Lamp will light up during step (4).


INSPECTION PROCEDURE