Description
DATA TROUBLE CODE: 71SYSTEM: EGR System Malfunction (California)
CIRCUIT DESCRIPTION
The exhaust gas recirculation 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 reduce NOx emissions.
The lift amount of the exhaust gas recirculation valve is controlled by a step motor operated by the engine control module. The engine control module operates the motor only a preprogrammed amount in response to the engine operating conditions.
Under the following conditions, exhaust gas recirculation is cut to maintain driveability:
- Engine coolant temperature below 53°C (127°F)
- During deceleration (throttle valve closed)
- Light engine load (amount of intake air very small)
- Engine speed over 4,000 rpm
- Engine idling
- Park/Neutral position switch on
DIAGNOSTIC TROUBLE CODE DETECTING CONDITION
- Open or short in exhaust gas recirculation step motor Circuit for 1 second or more.
OR
- Exhaust gas recirculation gas temperature is 65°C (149°F) or below for 1 - 4 minutes under conditions below: (2 trip detection logic)
- Engine coolant temperature : 65°C (149°F) or more.
- Exhaust gas recirculation operation possible (EX. A/T in 3rd speed, A/C ON, 60 mph, flat road.)
TROUBLE AREA
- Open or short in exhaust gas recirculation step motor circuit.
- Engine control module.
OR
- Open in exhaust gas recirculation gas temperature sensor circuit.
- Engine control module.
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.
1. Disconnect the EFI fuse (30 A) for 10 seconds or more with Ignition Switch OFF. Initiate test mode (Connect terminal TE2 and E1 of Data Link Connector 1 or 2 with Ignition Switch OFF).
2. Start the engine and warm up.
3. After the engine is warmed up, let it idle for 3 minutes.
4. With the A/C ON and transmission in 3rd speed drive at 55 - 60 mph for 4 min or less.
NOTE: If the conditions in this test are not strictly followed, detection of the malfunction will not be possible. If a malfunction exists, the malfunction indicator lamp will light up during step 4.
Malfunction Indicator Lamp
Normal Mode On
Test Mode On