DME Temperature Gauge and Sensor – Troubleshooting and Testing

Overview

This procedure tests the DME temperature sensor on the Porsche 944  (16v engine), which provides critical engine temperature data to the Digital Motor Electronics (DME) system for fuel mixture control. An accurate DME temperature sensor ensures proper engine performance, as incorrect readings can cause overly rich (high resistance) or lean (low resistance) fuel mixtures. This test measures sensor resistance at specific temperatures and assumes the dashboard coolant temperature gauge is functioning correctly. If you suspect the dashboard gauge is faulty, complete the Coolant Temperature Gauge and Sensor Testing procedure first.

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Tools Required

• Multimeter
• Test leads
• Non-contact thermometer (optional, for surface temperature checks)

Required Additional Procedures

Steps in these procedures are required to complete this process:

• Coolant Temperature Gauge and Sensor Testing

Step-by-Step Procedure

Step 1: Prepare the Vehicle and Tools

1. Park the Porsche 944 on a level surface and engage the parking brake.
2. Ensure the engine is off and the ignition is in the OFF position.
3. Gather the multimeter, test leads, and an optional non-contact thermometer for surface temperature checks.

Step 2: Test DME Temperature Sensor at Ambient Temperature

4. Locate the DME computer, typically under the passenger-side footwell or behind the center console on the Porsche 944 (16v engine).
5. Carefully disconnect the DME computer electrical connector.
6. Connect the multimeter (set to ohms) between terminal 13 on the disconnected DME plug and a grounding point in the engine compartment, such as a clean, unpainted bolt or chassis ground.
7. Measure the resistance and compare it to the values in the table below for ambient temperatures (15–30°C / 59–86°F). For example, at 15°C (59°F), expect approximately 3.3 k-ohms; at 30°C (86°F), expect approximately 1.46 k-ohms.

Step 3: Warm Up the Engine

8. Reconnect the DME computer electrical connector securely.
9. Start the engine and let it run until the dashboard coolant temperature gauge indicates approximately 80°C (176°F). This may take several minutes, depending on ambient conditions.
10. If you suspect the dashboard gauge is inaccurate, use a non-contact thermometer to measure the surface temperature on the engine block near the DME temperature sensor (located near the cylinder head) to confirm it’s around 80°C (176°F).

Step 4: Test DME Temperature Sensor at Operating Temperature

11. Turn the engine off and ensure the ignition is in the OFF position.
12. Disconnect the DME computer electrical connector again.
13. Connect the multimeter between terminal 13 on the DME plug and ground, as described in Step 2.
14. Turn the ignition switch to the ON position (do not start the engine) and verify the dashboard gauge still reads approximately 80°C (176°F). Alternatively, use the non-contact thermometer to confirm the block surface temperature near the sensor.
15. Measure the resistance and compare it to the value in the table below for 80°C (176°F), which should be 280–360 ohms.

Step 5: Evaluate Results and Troubleshoot

16. If the measured resistances match the values in the table (within tolerance), the DME temperature sensor is functioning correctly.
17. If the resistances are higher than specified (e.g., >3.3 k-ohms at 15°C or >360 ohms at 80°C), the sensor may cause a richer fuel mixture and should be replaced with a new DME temperature sensor (944 606 145 00).
18. If the resistances are lower than specified (e.g., <1.46 k-ohms at 30°C or <280 ohms at 80°C), the sensor may cause a lean fuel mixture and should be replaced with a new DME temperature sensor (944 606 145 00).
19. If issues persist after replacement, inspect the DME wiring, connectors, or dashboard gauge. Consult a professional if needed.

Post Procedure Checklist

• Ensure the DME computer electrical connector is securely reconnected.
• Verify no tools or test leads are left in the vehicle.
• Start the engine and confirm the dashboard coolant temperature gauge reads normally (typically 80–100°C during driving).
• Check for any warning lights, error codes, or abnormal engine performance (e.g., rough idling, poor fuel economy).

Sources

• Clark’s Garage
• Pelican Parts
• Porsche 944 Workshop Manual, Volume 1
• Youtube