EG–453 ENGINE – 2JZ–GE ENGINE TROUBLESHOOTING DTC 71 EGR System Malfunction 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 load. If even one of the following conditions is fulfilled, the VSV is turned ON by a signal from the ECM. This results 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 (122°F) • During deceleration (Throttle valve closed) • Light engine load (amount of intake air very small). • Engine speed over 5,200 rpm • Traction control is operating F16895 Throttle Valve VSV ECM Air Intake Chamber EGR Valve EGR Vacuum Modulator Exhaust Gas EGR Gas Temp. Sensor DTC No. | Diagnostic Trouble Code Detecting Condition | Trouble Area 71 | EGR gas temp. is 70°C (158°F) or less for 1 ~ 4 min. under conditions (a) and (b): (2) trip detection logic)* (a) Engine coolant temp.: 63°C (145°F) or more (b) EGR operation possible (Example A/T in 3rd speed (5th for M/T), A/C ON, 96 km/h (60 mph), Flat road) | • Open in EGR gas temp. sensor circuit • Short in VSV circuit for EGR • EGR hose disconnected, valve stuck • Clogged EGR gas passage • ECM (See page EG–397). 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 by confirming that diagnostic trouble code is no longer detected.