Easy one-page printout for the garage or repair shop
This summary uses the existing diagnostic information shown in full below.
The car's computer is saying that the part that helps control the engine's temperature is not working right. It's like when your room heater is stuck on high and won't turn down.
This code indicates that there is a problem with the electrical circuit that controls the map cooling thermostat, which is responsible for regulating engine temperature.
The P1620 code is triggered when the Engine Control Module (ECM) detects a high voltage signal from the map cooling thermostat control circuit. This typically means there is an issue with the wiring, the thermostat itself, or the ECM.
• Check Engine Light is on
• Engine may overheat
• Poor fuel economy
• Faulty map cooling thermostat
• Wiring issues in the thermostat circuit
• Faulty Engine Control Module (ECM)
ECM: Engine Control Module
OBD-II: On-Board Diagnostics II
• Use an OBD-II scanner to confirm the code.
• Inspect the wiring and connectors for damage.
• Test the map cooling thermostat for proper operation.
• Repair or replace damaged wiring or connectors.
• Replace the map cooling thermostat if faulty.
• Replace or reprogram the ECM if necessary.
• OBD-II scanner
• Multimeter
• Basic hand tools
$150 - $500
Moderate
• BMW 3 Series
• BMW 5 Series
• Mini Cooper
• Regular maintenance checks
• Ensure proper coolant levels
• Inspect wiring regularly
Sensor Issue
• Have the vehicle inspected by a professional.
• Avoid driving the vehicle if overheating occurs.
Check with your vehicle manufacturer for warranty coverage on the thermostat.
This code has been more prevalent in vehicles with advanced cooling systems introduced in the early 2000s.
Moderate – Address the issue to prevent engine overheating.
Ignoring this code may lead to engine damage or failure.
• Engine at normal operating temperature
• Vehicle stationary with ignition on
The map cooling thermostat is typically located near the engine block, connected to the cooling system.
Q: Can I drive with a P1620 code?
A: It's not recommended to drive for long periods with this code as it may lead to engine overheating.
Q: How do I reset the P1620 code?
A: You can reset the code with an OBD-II scanner, but it's important to fix the underlying issue first.
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Universal · Digital multimeter
A solid entry-level multimeter for voltage, continuity, resistance, and basic electrical troubleshooting.
Helpful for checking voltage drops, grounds, and basic circuit health when modules are not communicating.
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Universal · Wire connectors and repair kit
Useful when diagnosis points toward damaged wiring, corroded terminals, or connector repairs.
Useful if diagnosis points toward damaged connectors, wiring, or terminal repairs.
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Fitment Required · Vehicle-fitment part
Relevant when coolant-temperature and warm-up faults indicate a thermostat-related issue.
Coolant-temperature and warm-up faults often lead to thermostat testing and replacement.
Thermostats are vehicle-specific and should be matched by engine and housing style.
View options on AmazonThese parts may be related to this fault category, but a code by itself does not confirm exact fitment or guarantee that replacing a part will solve the problem.