MAP-Controlled Engine Cooling Thermostat, Checking

Diagnostic Procedures

Map-Controlled Engine Cooling Thermostat, Checking

Special tools, testers and auxiliary items required

• Multimeter (VAG1526) or Multimeter (VAG1715)

• Connector test kit (VAG1594)

• Wiring diagram

Test Prerequisites

• Fuses in E-box (plenum chamber, left) must be OK:





• Battery voltage must be at least 11.5 volts.

• All electrical consumers such as, for example, lights and rear window defroster must be switched off.

• For vehicles with automatic transmission, selector lever must be in P.

• If vehicle is equipped with an A/C system, it must be switched off.

• Ground (GND) connections between engine and chassis must be OK.

• Ignition is switched off.

Test Sequence

- Disconnect 2-pin connector from Map Controlled Engine Cooling Thermostat (F265).

- Using adapter cables, measure heating wire resistance at Map Controlled Engine Cooling Thermostat (F265).Specified value at 25 °C: 14.0 to 18.0 ohms

If specified value is not obtained:

- Replace Map Controlled Engine Cooling Thermostat (F265).

- Erase DTC memory of Engine Control Module (ECM) --> [ Diagnostic Mode 04 - Erase DTC Memory ] Diagnostic Modes 01 - 09, Diagnostic mode 4: Reset/erase diagnostic data.

- Generate readiness code --> [ Readiness Code ] Monitors, Trips, Drive Cycles and Readiness Codes.

If specified value is obtained:

Checking Voltage Supply

- Connect multimeter to terminal 1 of 2-pin connector and Ground (GND) for voltage measurement.

- Switch ignition on.

Specified value: at least 11.5 V

- Switch ignition off.

If specified value is not obtained:

- Check wire via Fuse (S11) to Power Supply Relay (Terminal 30, B+) Relay 2 (J689) and Power Supply (Terminal 30, B+) Relay (J317) according to wiring diagram:

- Erase DTC memory of Engine Control Module (ECM) --> [ Diagnostic Mode 04 - Erase DTC Memory ] Diagnostic Modes 01 - 09.

- Generate readiness code --> [ Readiness Code ] Monitors, Trips, Drive Cycles and Readiness Codes.

If specified value is obtained:

- Check Control Module Wires.

Control Module Wires, Checking

- Connect test box ((VAG1598/42)) to Engine Control Module (ECM) (J623) wiring harness using adapter cable ((VAG1598/39-1)) , connecting test box for wiring test.

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





Terminal 2+socket 45

Wire resistance: max. 1.5 ohms

- Also check wire for short circuit to vehicle Ground (GND) and to B+.

Specified value: infinite ohms

If no malfunctions are detected in the wires and the heating wire resistance was OK:

- Replace Engine Control Module (ECM) (J623).

- Generate readiness code --> [ Readiness Code ] Monitors, Trips, Drive Cycles and Readiness Codes.