Diag. Code 71 EGR System Malfunction CIRCUIT DESCRIPTION. TR-92 ENGINE TROUBLESHOOTING - Circuit Inspection

Transcription

1 TR-92 EINE TROUBLESHOOTI - Circuit Inspection Diag. Code 71 EGR System Malfunction CIRCUIT DESCRIPTION The EGR system is designed to recirculate the exhaust gas properly controlled according to the driving condition 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 ECU. This results in atmospheric air acting on the EGR valve, closing the EGR valve and shutting off the exhaust gas (EGR cut-off). Coolant temperature below predetermined level. During deceleration (throttle valve closed). Light engine load (amount of intake air very small). Engine speed over 4000 rpm. Engine racing (neutral start switch turned on). Code No. Diagnosis Trouble Area 71 *: See page TR-19. With engine warmed up and EGR operation possible (ECT in 3rd speed, A/C ON, mph), code is displayed when EGR gas temp. sensor is 65 C or less when vehicle is driven for 90 sec. (2 trip detection logic)* Open in EGR gas temp. sensor circuit Short in VSV circuit for EGR EGR hose disconnected, valve stuck ECU

2 EINE TROUBLESHOOTI - Circuit Inspection TR-93 CIRCUIT DESCRIPTION (Cont d) DIAGNOSIS CODE DETECTION DRIVI PATTERN Purpose of the driving pattern. (a) After the diag. code is erased, the malfunction is reproduced and the diag. code is recorded again. (b) To check that the malfunction is cleared once the repair is completed (confirm that diag. code is no longer detected). Malfunction: Short in VSV Circuit for EGR, Loose EGR Hose, Valve Stuck Initiate test mode (See page TR-10 ). Start engine and warm engine up. After engine is warmed up, let it idle for 3 min. With the A/C ON and transmission in D range (O/D OFF), drive at mph for 4 min. HINT: If a malfunction exists, the CHECK engine warning light will light up at 1-4 min. of driving at mph ( km/h). NOTICE: If the conditions in this test are not strictly observed, detection of the malfunction will not be possible.

3 TR-94 DIAGNOSTIC CHART EINE TROUBLESHOOTI - Circuit Inspection 1 Check for air leakage in EGR system (See page EC-9 ). Repair air leakage. 2 Check EGR vacuum modulator (See page EC-10, 11 ). Repair or replace EGR vacuum modulator. 3 Check VSV with cold engine. Check VSV and EGR vacuum modulator with warm engine (See page EC-10 ). 4 Check EGR valve (See page EC-1 1). Repair or replace EGR valve. Proceed to next circuit inspection shown on matrix chart (See page TR-26 ). *1: When diag. code 71 is displayed, go to step 8. Check VSV for EGR (See page 5 Repair or replace VSV for EGR. EC-12 ). 6 Check voltage between terminal EGR of engine & ECT ECU connector and body ground. Repair or replace EGR valve. 7 Check harness and connector between engine & ECT ECU and VSV for EGR, VSV for EGR and EFI main relay (See page IN-27 ). Repair or replace harness or connector. Check and replace engine & ECT ECU. 8 Check EGR gas temp. sensor. Replace EGR gas temp. sensor. Check and replace engine & ECT ECU.

4 WIRI DIAGRAM EINE TROUBLESHOOTI - Circuit Inspection TR-95

5 TR-96 WIRI ROUTI EINE TROUBLESHOOTI - Circuit Inspection

6 INSPECTION PROCEDURE EINE TROUBLESHOOTI - Circuit Inspection TR-97 1 Check for air leakage in EGR system (See page EC-9 ). C Check for air leakage in EGR system. Repair air leakage. 2 Check EGR vacuum modulator (See page EC-10, 11). Repair or replace EGR vacuum modulator. 3 Check VSV with cold engine. Check VSV and EGR vacuum modulator with warm engine (See page EC-10 ). Go to step 5. 4 Check EGR valve (See page EC-1 1). Proceed to next circuit inspection shown on matrix chart (See page TR-26 ). *1 Repair or replace EGR valve. *1: However, when diag. code 71 is displayed, go to step. 8

7 TR-98 EINE TROUBLESHOOTI - Circuit Inspection 5 Check VSV for EGR (See page EC-12 ). Repair or replace VSV for EGR. 6 Check voltage between terminal EGR of engine & ECT ECU connector and body ground. P C (1) Remove RH lower pad. (2) Start the engine. (3) Warm up engine to normal operating temperature. Measure voltage between terminal EGR of engine & ECT ECU connector and body ground, when engine is following conditions. Condition A: Idling Condition B: Fully depress the parking brake pedal, and while strongly pressing the brake pedal with your left leg, shift from N range to D range and control the accelerator pedal with your right leg at the engine speed is 1400 rpm. Engine Condition Condition A Condition B Voltage Battery Voltage Approx. 0V Notice Do not perform the operation continuously for longer than 5 seconds. Repair or replace EGR valve. 7 Check harness and connector between engine & ECT ECU and VSV for EGR, VSV for EGR and EFI main relay (See page IN-27 ). Repair or replace harness or connector. Check and replace EGR valve.

8 EINE TROUBLESHOOTI - Circuit Inspection TR-99 8 Check EGR gas temp. sensor. P Disconnect EGR gas temp. sensor connector (See page FI-78 ). C Measure resistance between terminals of EGR gas temp. sensor connector. Resistance: k at 50 C (122 F) k at 100 C (212 F) k at 150 C (302 F) Replace EGR gas temp. sensor. Check and replace engine & ECT ECU.