Code 39
EGR TEMPERATURE SENSOR CIRCUIT -DTC 39
The ECM looks for a low EGR temperature signal when the EGR solenoid vacuum valve is open and a high EGR temperature signal when the EGR solenoid vacuum valve is closed. In addition, the ECM looks for an over-temperature condition when EGR is enabled.
The ECM monitors the temperature at the intake manifold EGR adapter to determine if exhaust gas is flowing when the engine is operating within the EGR operating envelope. When EGR is disabled by the ECM, 5 minutes are allowed for the system to cool down.
EGR Operating Envelope:
The EGR temperature sensor is a "negative temperature coefficient" (NTC) thermistor in which the resistance decreases as the temperature increases. The ECM applies 5 volts to the sensor and monitors for a voltage decrease when exhaust gas flows.
The ECM will flag DTC 39 if the EGR temperature signal is outside a limit (higher or lower) when EGR is enabled or disabled.
Conditions Required For DTC 39 Flagging
Engine coolant temp - Greater than 82°C (180°F).
Throttle position - Within the expected range for the engine speed.
Engine speed - 1700-3000.
Load site range - 2-7 (requires road test)
EGR enabled EGR temperature greater than 275°C (525°F) (temp. sensor voltage signal less than 0.95 V)
Response time - 64 milliseconds.
EGR enabled - EGR temperature less than 100°C (212°F) (temp. sensor voltage signal greater than 4.72 V).
Response time - 1 minute.
EGR disabled - EGR temperature greater than 50°C (122°F) (temp. sensor voltage less than 4.96 V).
Response time - 5 minutes.
Limp Home Default
If DTC 39 Is Flagged, EGR Is Disabled.
Possible Faults
- Blockage in EGR transfer pipe between EGR valve and intake manifold.
- Blockage in intake manifold EGR adapter.
- Disconnected, leaking or blocked vacuum hose to EGR solenoid vacuum valve or EGR valve.
- Defective EGR solenoid vacuum valve.
- Defective EGR valve.
- Defective EGR temperature sensor.
- Open or short circuit wiring.
Diagnostic Notes
1. The EGR temperature sensor signal voltage can be monitored and the signals stored using the PDU Datalogger. There is no PDU Datalogger trigger.
2. Test for a DTC reoccurrence by road testing the vehicle at highway speed. Maintain a steady throttle position and engine speed between 1700 and 3000 rpm for more than 1 minute.
3. Test for EGR transfer pipe or intake manifold adapter blockage by manually lifting the EGR valve diaphragm while the engine is running at 1000 rpm. If the engine speed decreases when the diaphragm is lifted. exhaust gas is flowing to the intake manifold.
WARNING: THE EGR VALVE IS HOT WHEN THE ENGINE IS RUNNING AND WILL BURN UNPROTECTED SKIN.
4. EGR Temperature Sensor temperature / resistance:
50°C (122°F) / 560-710 kilo ohms
100°C (212°F) / 76-94 kilo ohms
5. XJ6 Sedan Range vehicles up to VIN 664940 - When replacing an oxygen sensor, install a splash shield (P/N C33139/4). All vehicles after this VIN, including XJS, are equipped with splash shields.
6. 1992 MY ON vehicles (ECM part number DBC 9622 ON): DTC 26 and 44 are inhibited when the fuel level is below approximately 2.5 gallons. A fuel level signal is input to the ECM on the yellow connector pin 6 from the fuel level sensor circuit. When the voltage is above 5.7 volts, the codes cannot be flagged.
Fuel Pressure Check
42-45 psi (vacuum disconnected from fuel pressure regulator).
34-38 psi at idle (vacuum connected to fuel pressure regulator).
Purge Valve Test, To Test For A Sticking Purge Valve:
- Disconnect the purge hose at the intake manifold adapter.
- Switch ignition ON; do not start the engine.
- Apply vacuum to purge hose; vacuum should hold. If the vacuum does not hold, the purge valve is stuck and should be replaced.
- Switch ignition OFF; vacuum should release after a few seconds. If the vacuum does not release, the purge valve is stuck and should be replaced.
Circuit Diagram
Circuit Diagram:
Flow Chart - DTC 39
�v�Flow Chart - DTC 39:
