With Generic Scan Tool
Engine Coolant Temperature (ECT) sensor, checking
Recommended special tools and equipment
- V.A.G 1526 multimeter or V.A.G 1715 multimeter
- V.A.G 1594 Connector test set
- Wiring diagram
Test requirements
- The respective fuses of Motronic Engine Control Module (ECM) -J220- must be OK:
- Parking brake must be engaged or else daylight driving lights will be switched on.
- Engine must be cold.
Function test
- Connect diagnostic tester. Diagnostic Tester, Connecting
- Switch ignition on.
- Under address word 33, select "Diagnostic mode 1: Checking measuring values."
- Select the measuring value "PID 05: Coolant temperature".
- Check specified value of coolant temperature:
If specified value is not obtained:
- Continue test according to the following table:
Indicated 1) Cause
approx. -40 degrees C Open circuit or short circuit to B+
approx. 143 degrees C Short circuit to Ground (GND)
1) If a temperature is indicated which differs greatly from ambient temperature of sensor, check sensor wires for contact resistance.
If specified value is obtained:
- Start engine and let run at idle. The temperature should climb uniformly
NOTE:
- The temperature increases in increments of 1.0 degrees C..
- If the engine shows problems in certain temperature ranges and if the temperature does not climb uniformly, the temperature signal is intermittent and the sensor should be replaced.
Continuation of test if indication is approx. -40 degrees C:
- Disconnect 4-pin connector from Engine Coolant Temperature (ECT) Sensor -G62- with Engine Coolant Temperature (ECT) Sensor -G2- (arrow)
Vehicles with engine code AHA
- Bridge terminals 1 + 3 of connector using the respective adapter cables and observe the indication on display.
Vehicles with engine code ATQ
- Bridge terminals 3 + 4 of connector using the respective adapter cables and observe the indication on display.
Continuation for all vehicles
If indication jumps to approx. 143 degrees C:
- End diagnosis and switch ignition off.
- Replace Engine Coolant Temperature (ECT) Sensor -G62- with Engine Coolant Temperature (ECT) Sensor -G2-, item 33 .
- Erase DTC memory of Engine Control Module (ECM), Diagnostic mode 4:Reset/erase diagnostic data.
- Generate readiness code. Monitors, Trips, Drive Cycles and Readiness Codes
If indication remains at approx. -40 degrees C:
- End diagnosis and switch ignition off.
- Check wires according to wiring diagram.
Continuation of test if indication is approx. 143 degrees C:
- Disconnect 4-pin connector from Engine Coolant Temperature (ECT) Sensor -G62- with Engine Coolant Temperature (ECT) Sensor -G2- (arrow)
If indication jumps to approx. -40 degrees C:
- End diagnosis and switch ignition off.
- Replace Engine Coolant Temperature (ECT) Sensor -G62- with Engine Coolant Temperature (ECT) Sensor -G2-, item 33 .
- Erase DTC memory of Engine Control Module (ECM), Diagnostic mode 4: Reset/erase diagnostic data.
- Generate readiness code. Monitors, Trips, Drive Cycles and Readiness Codes
If indication remains at approx. 143 degrees C:
- End diagnosis and switch ignition off.
- Check wires according to wiring diagram.
Checking wiring
- Connect test box to control module wiring harness, connect test box for wiring test. Test Box, Connecting For Wiring Test
Vehicles with engine code AHA
- Check wires between test box and 4-pin connector for open circuits according to wiring diagram.
Terminal 1 + socket 53
Terminal 3 + socket 67
Wire resistance: max: 1.5 Ohms
Vehicles with engine code ATQ
- Check wires between test box and 4-pin connector for open circuits according to wiring diagram.
Terminal 3 + socket 108
Terminal 4 + socket 93
Wire resistance: max: 1.5 Ohms
Continuation for all vehicles
- Also check wires for short circuits to each other, to vehicle Ground (GND) and to B+.
Specified value: Infinity Ohms
If no malfunctions are found in wires:
Vehicles with engine code AHA
- Perform a resistance measurement at Engine Coolant Temperature (ECT) Sensor -G62- terminal 1 (signal) and 3 (Ground -GND-).
Vehicles with engine code ATQ
- Measure resistance at Engine Coolant Temperature (ECT) Sensor - G62-, terminals C (signal) and D (Ground -GND-).
Continuation for all vehicles
Range A displays resistance values for the temperature range of 0 to 50 degrees C, range B displays resistance values for the temperature range of 50 to 100 degrees C.
Read-out examples:
- 30 degrees C is in range A and corresponds to a resistance of 1.5 to 2.0 kOhms
- 80 degrees C is in range B and corresponds to a resistance of 275 to 375 kOhms
If specified value is not obtained:
- Replace Engine Coolant Temperature (ECT) Sensor -G62- with Engine Coolant Temperature (ECT) Sensor -G2-, item 33 .
- Erase DTC memory of Engine Control Module (ECM), Diagnostic mode 4: Reset/erase diagnostic data.
- Generate readiness code. Monitors, Trips, Drive Cycles and Readiness Codes
If no malfunctions are detected in the wires and the resistance values are OK:
- Replace Motronic Engine Control Module (ECM) -J220-.