Mechanics

CODE 71

1995 Toyota Corolla

Engine Mechanical problem
1995 Toyota Corolla 4 cyl Front Wheel Drive Automatic 113000 miles

my car is a 1995 corolla 1.8 the problem new egr valve include the sensor all parts are new in the egr check engine light on continues on codes are clear my friend say computer is bad
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Janice27
May 9, 2009.



This is what my book say about the code
read it see if it helps let me know
CODE 71 - EXHAUST GAS RECIRCULATION (EGR) SYSTEM MALFUNCTION
CAUTION: If ECM replacement is instructed in following testing, always ensure ECM harness connector and ground circuit are okay. If either are suspect, repair and repeat testing to confirm ECM malfunction.

Circuit Description
The EGR system recirculates exhaust gas through intake system to reduce combustion temperature and NOx emissions. The amount of EGR valve opening is regulated by the EGR vacuum modulator according to engine load. Vacuum source to valve is controlled by the Vacuum Switching Valve (VSV), which is operated by ECM.
The EGR valve is closed (VSV on) under the following conditions: Coolant temperature 122 °F (50 °C).
Vehicle under deceleration.
Light engine load.
Engine racing.
Code is set when EGR gas temperature is 140 °F (60 °C) or less for 50 seconds when engine coolant is 140 °F (60 °C) or more. Possible causes are: EGR gas temperature sensor open circuit.
EGR VSV open or short circuit.
EGR vacuum hose disconnected.
Clogged EGR passage.
ECM.
NOTE: Conduct following test drive to simulate trouble code detecting condition after code is recorded, and to confirm malfunction is corrected after repair.

CAUTION: If test conditions are not strictly followed, detection of malfunction will not be possible.

Code Detection Test Drive
Ensure ignition switch is off. Disconnect EFI fuse for 10 seconds or more. Reinstall fuse. Connect jumper wire between DLC1 terminals TE2 and E1. Start engine and operate till at normal operate temperature.
Idle engine for 3 minutes. Turn A/C on. Drive vehicle at 55-60 MPH on flat road for 4 minutes. If malfunction exists, MIL will illuminate during test drive.
Diagnosis & Repair
Warm engine to normal operating temperature. Access ECM behind center console under passenger side floor mat. Using DVOM, backprobe harness connector. Measure voltage between EGR terminal and ground. See Fig. 5.
If 9-14 volts is present, go to step 4). If 9-14 volts is NOT present, remove EGR VSV. VSV is beside EGR valve. Measure resistance between valve terminals. If resistance is 37-44 ohms, go to next step. If resistance is NOT 37-44 ohms, replace VSV.
Inspect circuit between EFI main relay and EGR VSV, and VSV and ECM for open or short. Repair as needed. If circuit is okay, replace ECM.
Inspect EGR system. See SYSTEM/COMPONENT TESTS - 1.8L article. Repair as needed. If system is okay, inspect EGR gas temperature sensor. See the SYSTEM/COMPONENT TESTS article. Replace as needed.
If sensor is okay, inspect circuit between EGR gas temperature sensor and ECM for open. Repair as needed. If circuit is okay, replace ECM and retest

BMRFIXIT
May 10, 2009.