DTC 71

DTC 71 EGR System Malfunction

System Schematic:

CIRCUIT DESCRIPTION
The EGR system is designed to recirculate the exhaust gas, controlled according to the driving conditions back into the intake air-fuel mixture. It helps to slow down combustion in the cylinder and thus lower the combustion temperature which, in turn, reduces the amount of NOx emission. 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 ON by a signal from the ECM. This resuits in atmospheric air acting on the EGR valve, closing the EGR valve and shutting off the exhaust gas (EGR cut-OFF).
- Engine coolant temp. below 50°C (1 22°F)
- During deceleration (throttle valve closed)
- Light engine load (amount of intake air very small)
- Engine speed over 4,800 rpm
- Manifold absolute pressure more than 120 kPa (1.2 kgf/sq.cm, 17.4 psi)





DETECTING CONDITION

DIAGNOSTIC TROUBLE CODE DETECTION DRIVING PATTERN

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

Detection Driving Pattern:

Malfunction: Open in EGR Gas Temp. Sensor Circuit

(1) Disconnect the EFI No. 1 fuse (30A) for 10 sec. or more, with IG switch OFF. Initiate test mode (Connect terminal TE2 and E1 of data link connector 2 with IG switch OFF).
(2) Start the engine and warm up.
(3) Idle the engine for 3 min.
(4) With the A/C ON and transmission in 5th position (A/T in 3rd speed) drive at 88 ~ 96 km/h (55 ~ 60 mph) for 4 min or less.

HINT: If a malfunction exists, the malfunction indicator lamp will light up during step (4).

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





WIRING DIAGRAM

Step 1:

Step 2:

Step 3:

Step 4:

Step 5:

Step 6:

INSPECTION PROCEDURE