Engine Coolant Temperature Sensor, Checking

Special tools and workshop equipment required 

• Multimeter VAG1526 or multimeter VAG1715
• Connector test kit VAG1594
• Wiring diagram

Test requirements 

• Fuses in E-box (in plenum chamber, left) must be OK: Refer to SYSTEM WIRING DIAGRAM
  Fig 1: Identifying Fuses In E-Box (In Plenum Chamber, Left)

  Courtesy of VOLKSWAGEN GROUP OF AMERICA, INC.
• Ground (GND) connections between engine and chassis must be OK.
• Parking brake must be engaged or else daylight driving lights will be switched on.
• For vehicles with automatic transmission, selector lever must be in P position.
• Engine must be cold.

Function test 

-- Connect diagnostic tester.

-- Switch ignition on.

-- Under address word 33, select "Diagnostic mode 1: Checking measured values."

-- Select the measuring value "PID 05: Coolant temperature".

-- Check specified value of coolant temperature:

PID		Diagnostic text		Specified value:
05:		Coolant temperature		approx. coolant temperature

If specified value is not obtained:

-- Continue test according to the following table:

Indicated  List Item:If a temperature is indicated which differs greatly from ambient temperature of sensor, check sensor wires for contact resistance.	Cause	Continue testing
approx. -40° C	Open circuit or short circuit to B+
approx. 140° 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 must

climb uniformly

-- Switch ignition off.

Continuation of test if indication is approx. -40° C: 

-- Disconnect 2-pin connector from Engine Coolant Temperature (ECT) Sensor -G62- (arrow).

-- Bridge terminals 1 + 2 of connector using the respective adapter cables and observe the indication on display.

If indication jumps to approx. 140° C: 

-- End diagnosis and switch ignition off.

-- Replace Engine Coolant Temperature (ECT) Sensor -G62-.

-- Erase DTC memory of Engine Control Module (ECM), Diagnostic mode 4: Reset/erase diagnostic data.

-- Generate readiness code.

If indication remains at approx. -40° C: 

-- End diagnosis and switch ignition off.

-- Check wires according to wiring diagram.

Continuation of test if indication is approx. 140° C: 

-- Disconnect 2-pin connector from Engine Coolant Temperature (ECT) Sensor -G62- (arrow).

If indication jumps to approx. -40° C: 

-- End diagnosis and switch ignition off.

-- Replace Engine Coolant Temperature (ECT) Sensor -G62-.

-- Erase DTC memory of Engine Control Module (ECM), Diagnostic mode 4: Reset/erase diagnostic data.

-- Generate readiness code.

If indication remains at approx. 140° 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.

-- Check wires between test box and 2-pin connector for open circuit according to wiring diagram.

Terminal 1+socket 93

Terminal 2+socket 108

Wire resistance: max. 1.5 Ω

-- Also check wires for short circuit to each other, to vehicle Ground (GND) and to B+.

Specified value: ∞ Ω

-- Erase DTC memory of Engine Control Module (ECM), Diagnostic mode 4: Reset/erase diagnostic data.

-- Generate readiness code.

If no malfunctions are found in wires:

-- Replace Engine Coolant Temperature (ECT) Sensor -G62-.

-- Erase DTC memory of Engine Control Module (ECM), Diagnostic mode 4: Reset/erase diagnostic data.

-- Generate readiness code.

If no malfunctions are detected in the wires and the resistance values are OK:

-- Replace Motronic Engine Control Module (ECM) -J220- ENGINE CONTROL MODULE, REPLACING .