BMW DTC P1621 – Map Cooling Thermostat Control Circuit Intermittent
DTC P1621 meaning on BMW
DTC P1621 on a BMW indicates an issue with the Map Cooling Thermostat Control Circuit being intermittent. This means that there is a problem with the circuit that controls the thermostat responsible for regulating the engine coolant temperature based on the map sensor input.
BMW DTC P1621 symptoms
Symptoms of DTC P1621 on a BMW may include:
- Engine overheating
- Decreased fuel efficiency
- Check Engine Light (CEL) illuminated on the dashboard
- Engine running too cold or too hot
BMW DTC P1621 causes
The potential causes of DTC P1621 on a BMW include:
- Faulty map cooling thermostat
- Wiring or connector issues in the thermostat control circuit
- Defective engine coolant temperature sensor
- ECU (Engine Control Unit) malfunction
BMW DTC P1621 seriousness
Ignoring DTC P1621 on a BMW can lead to serious engine problems such as overheating, which may cause engine damage or even failure. It is important to address this issue promptly to prevent further complications.
How to diagnose DTC P1621 on BMW
To diagnose DTC P1621 on a BMW, you can perform the following steps:
- Use a diagnostic scanner to retrieve the fault codes from the ECU
- Inspect the map cooling thermostat and its wiring for any visible damage
- Check the engine coolant temperature sensor for proper operation
- Test the thermostat control circuit for continuity and proper voltage
How to fix DTC P1621 on BMW
To fix DTC P1621 on a BMW, you may need to:
- Replace the faulty map cooling thermostat
- Repair or replace any damaged wiring or connectors in the thermostat control circuit
- Replace the engine coolant temperature sensor if necessary
- If the ECU is found to be faulty, it may need to be reprogrammed or replaced
How to erase DTC P1621 on BMW
To erase DTC P1621 on a BMW, you can:
- Use a diagnostic scanner to clear the fault codes stored in the ECU
- After fixing the underlying issue, drive the vehicle to allow the ECU to perform a self-check and verify that the fault code does not return
Recommended tools & DTC Scanners for BMW
Best Diagnostic App for modern BMWs: BimmerLink
Recommended Bluetooth adapter for Bimmerlink: OBDLink CX
Cable adapter for Bimmerlink: Enet Cable USB Type C
For older BMWs we recommend: Autel AutoLink AL319 (2024 version)
Easy-to-use Multimeter for reliable diagnostics: AstroAI Auto-ranging Multimeter
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