MAP Controlled Engine Cooling Thermostat

Special Tools And Workshop Equipment Required 

• multimeter.
• Wiring diagram.

Test requirements

• The Map Controlled Engine Cooling Thermostat -F265- fuse OK.
• The Motronic Engine Control Module (ECM) Power Supply Relay -J271- fuse OK.
• Battery voltage at least 12.5 V.
• All electrical consumers switched off (radiator fan must NOT run during test).
• A/C switched off.
• The ignition switched off.

Test procedure

-- Perform a preliminary check to verify the customers complaint. Refer to PRELIMINARY CHECK .

Start diagnosis

Procedure

-- Disconnect the Map Controlled Engine Cooling Thermostat -F265- electrical harness connector -1-.

Checking internal resistance

-- Using a multimeter, check the Map Controlled Engine Cooling Thermostat -F265- terminals 1 to 2 for resistance.

Specified value: 25 to 35 Ω (at approx. 20° C)

If the specified value was not obtained:

-- Replace the Map Controlled Engine Cooling Thermostat -F265-. Refer to appropriate service information.

If the specified value was obtained:

Checking voltage supply

Switch the ignition on.

-- Using a multimeter, check the Map Controlled Engine Cooling Thermostat -F265- electrical connector terminal 1 to Ground (GND) for voltage.

Specified value: approx. battery voltage.

Switch the ignition off.

If the specified value was not obtained:

-- Check the wiring from the Map Controlled Engine Cooling Thermostat -F265- electrical connector terminal 1 to the fuse SA15 for a open circuit.

-- Check the electrical harness connector for damage, corrosion, loose or broken terminals.

-- If necessary, repair the wiring connection.

If no malfunctions are found in the wiring:

Checking wiring

If the manufacturers test box is being used, perform the following step.

-- Install the test box.

If the manufacturers test box is not being used, perform the following step.

-- Remove the Motronic Engine Control Module (ECM) -J623-. Refer to appropriate service information.

-- Using a multimeter --, check the Map Controlled Engine Cooling Thermostat -F265- electrical harness connector terminal 2 to the Motronic Engine Control Module (ECM) -J623- electrical harness connector T91 for an open circuit.

Map Controlled Engine Cooling Thermostat -F265- electrical harness connector terminal	Motronic Engine Control Module (ECM) -J623- electrical connector T91 terminal
2	74

Specified value: 1.5 Ω Max.

If the specification was not obtained:

-- Check the wiring for a short circuit to Battery (+), or an open circuit.

-- Check the electrical harness connector for damage, corrosion, loose or broken terminals.

-- If necessary, repair the faulty wiring connection.

If no malfunction is detected in the wiring:

-- Replace the Motronic Engine Control Module (ECM) -J623- Refer to appropriate service information.

Final procedures

After the repair work, the following work steps must be performed in the following sequence:

1. Check the DTC memory. Refer to DIAGNOSTIC MODE 03 - READ DTC MEMORY .
2. If necessary, erase the DTC memory. Refer to DIAGNOSTIC MODE 04 - ERASE DTC MEMORY .
3. If the DTC memory was erased, generate readiness code. Refer to READINESS CODE .