Description
DATA TROUBLE CODE: 71SYSTEM: EGR System Malfunction
WIRING DIAGRAM
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 ON by a signal from the engine control module (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 temperature below 60°C (140°F).
- During deceleration (throttle valve closed).
- Light engine load (amount of intake air very small).
- Engine speed over 4,400 rpm.
DIAGNOSTIC TROUBLE CODE DETECTING CONDITION
EGR gas temperature is at or below a predetermined temperature for 50 seconds under conditions (a) and (b).
(2 trip detection logic)
Monitors, Trips, Drive Cycles and Readiness Codes
(a) Engine coolant temperature: 80°C (176°F) or more.
(b) EGR operation possible (e.g. A/T in 3rd speed (5th for M/T), 55 ~ 60 mph (88 ~ 96 km/h), Flat road).
TROUBLE AREA
- Open in EGR gas temperature sensor circuit.
- Short in VSV circuit for EGR.
- EGR hose disconnected. valve stuck.
- Clogged EGR gas passage.
- Engine control module
TROUBLE CODE DETECTION DRIVING PATTERN
Malfunction: Open in EGR gas temperature sensor circuit
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.
Driving Pattern For Detecting DTC 71:
1. Disconnect the EFI fuse (15 A) for 10 sec. or more, with 16 switch OFF. Initiate test mode (Connect terminals TE2 and E1 of data link connector 1 with 16 switch OFF).
2. Start the engine and warm up.
3. After the engine is warmed up, let it idle for 3 min.
4. With the A/C ON and transmission in 5th gear (A/T in "D" position), drive at 55 ~ 60 mph (88 ~ 96 km/h) for 4 min. or less.
HINT: If a malfunction exists, the Malfunction Indicator Lamp will light up during step 4.
NOTE: If the conditions in this test are not strictly followed, detection of the malfunction will not be possible.