In 2021, BMW sold 821134 vehicles in China, ranking first among luxury car brands. As a popular product in the market, BMW electronic water pump has high requirements for installation steps and coolant quality, and faults in other components of the cooling system can also lead to misjudgment of electronic water pumps by repair shops. Today, based on our past experience, Jianke engineers will explain in detail the fault code analysis, fault causes, inspection steps, and solutions of ten BMW electronic water pumps for your reference and reference.

01

Fault code: 20A901

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1. Fault content

Engine cooling system, reduced power operation: Identify coolant pump causing coolant loss.

2. Fault Cause Analysis

The diagnostic system monitors the status of the coolant pump as' running without lubrication 'to identify the fault.

3. Troubleshooting methods (in order)

A. Check the liquid level in the water storage tank. If the liquid level is found to be low, check the cooling circuit for leaks.

B. Perform exhaust operation on the cooling circulation pipeline to eliminate the dry running of the water pump caused by air.

C. Replace the same model of water pump.

02

Fault code: 20A902

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1. Fault content

Engine cooling system, low power operation: The supply voltage of the coolant pump is too low.

2. Fault Cause Analysis

When the ECU monitors the power supply voltage of the water pump in real-time, this fault is recorded when the water pump feedback power supply voltage is too low.

3. Troubleshooting methods (in order)

A. Check if the voltage of the car battery is within the normal range (after starting, the voltage should be between 12~14V).

B. Unplug the water pump plug, check if there are signs of oxidation and burning on the plug, measure whether the voltage of the plug's power supply terminal (the thickest two wires) is the same as the battery voltage. If it is not the same, check the circuit. If it is the same, check the contact resistance between the plug and the water pump plug, or directly replace the wiring harness plug. Most of these can solve this problem.

C. Replace the same model of water pump.

03

Fault code: 20A904

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1. Fault content

Engine cooling system, reduced power operation: coolant pump exceeds temperature limit 1.

2. Fault Cause Analysis

The ECU monitors the internal control system temperature of the water pump in real-time, and records this fault when the internal control system temperature is too high.

Reason: Water pump over temperature protection, most of which are intermittent faults. Generally, the diagnosis computer can clear them and solve them without intervention.

3. Troubleshooting methods (in order)

A. Stop the engine first.

B. Wait for 30 minutes and restart.

C. Clear the fault code.

D. After waiting for 1 hour, this fault does not occur and no intervention is required.

E. If the overheating fault occurs again, please disassemble the water pump and check if the impeller is stuck, and if the antifreeze is deteriorated or dirty. If there are any abnormalities, try to eliminate them and see if the problem is resolved.

F. Replace the same model of water pump.

04

Fault code: 20A908

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1. Fault content

Engine cooling system, reduced power operation: coolant pump exceeds temperature limit 2.

2. Fault Cause Analysis

The ECU monitors the internal control system temperature of the water pump in real-time, and records this fault when the internal control system temperature is too high.

Reason: Water pump over temperature protection, most of which are intermittent faults that can be resolved after clearing without intervention.

3. Troubleshooting methods (in order)

A. Stop the engine first.

B. Wait for 30 minutes and restart.

C. Clear the fault code.

D. After waiting for 1 hour, this fault does not occur and no intervention is required.

E. If the overheating fault occurs again, please disassemble the water pump and check if the impeller is stuck, and if the antifreeze is deteriorated or dirty. If there are any abnormalities, try to eliminate them and see if the problem is resolved.

F. Replace the same model of water pump.

05

Fault code: 3779/20A802

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1. Fault content

Engine cooling system: coolant pump disconnected due to high voltage.

2. Fault Cause Analysis

The ECU records this fault after receiving data from the water pump that an overpressure occurred.

3. Troubleshooting methods (in order)

A. Check if the voltage of the power supply line is normal and eliminate overvoltage protection caused by abnormal generator power supply.

B. Replace the same model of water pump.

06

Fault code: 20AA04/CD9304/378F

1. Fault content

BSD information; Electric coolant pump: missing.

2. Fault Cause Analysis

When the ECU cannot receive the response information from the water pump, this fault is recorded.

3. Troubleshooting methods (in order)

A. Check if the power supply voltage of the water pump should be ≥ 9V and less than 9V, and check if there is a power loss.

B. Check if there is an open circuit or poor contact in the wiring from the ECU to the water pump on the bus (adjacent to the water pump ground wire); The normal voltage of the bus is between 7-11V.

C. Check if the water pump harness connector has good contact.

D. Replace the same model of water pump (when the above troubleshooting cannot eliminate the problem, the same below).

07

Fault code: CD9010

1. Fault content

LIN information; Electric coolant pump: missing.

2. Fault Cause Analysis

When the ECU cannot receive the response information from the water pump, this fault is recorded.

3. Troubleshooting methods (in order)

A. Check if the power supply voltage of the water pump should be ≥ 9V, and if it is less than 9V, check if there is a power loss.

B. Check if there is an open circuit or poor contact in the wiring from the ECU to the water pump on the bus (adjacent to the water pump ground wire); The normal voltage of the bus is between 7-11V.

C. Check if the water pump harness connector has good contact.

D. Replace the same model of water pump.

08

Fault code: 20A701/3792

1. Fault content

Engine cooling system: The coolant pump speed exceeds the tolerance range.

2. Fault Cause Analysis

When the actual speed feedback from the water pump during operation deviates too much from the speed given by the ECU, this fault is recorded.

3. Troubleshooting methods (in order)

A. Check if the voltage of the water pump power supply circuit is stable, and if it is abnormal, check the circuit.

B. Exhaust the cooling circulation pipeline to eliminate speed fluctuations caused by air.

C. Check the water tank and coolant for dirt or solid particle debris, thoroughly clean the pipeline to eliminate impurities (scale, particles, oil, etc.) that may cause the water pump to become stuck.

D. Check if the water pump harness connector has good contact.

E. If using BMW original concentrate, it must be diluted with pure water according to the recommended proportion by the manufacturer before use.

F. Replace the same model of water pump.

09

Fault code: 20A804

1. Fault content

Engine cooling system: coolant pump shut down due to lock up.

2. Fault Cause Analysis

After receiving feedback from the water pump that there is a blockage, the ECU records this fault.

Reason: Locked rotor protection or triggering of overcurrent protection.

3. Troubleshooting methods (in order)

A. Check the cooling circulation pipeline for blockages and eliminate excessive load caused by pipeline blockages.

B. Check the thermostat on the cooling circulation pipeline to eliminate excessive load caused by the failure of the thermostat.

C. Perform exhaust operation on the cooling circulation pipeline to eliminate abnormal startup caused by air.

D. Disassemble the cooling water pump and check if the mechanical part of the water pump is stuck.

E. If using BMW original concentrate, it must be diluted with pure water according to the recommended proportion by the manufacturer before use.

F. Replace the same model of water pump.

ten

Fault code: 20AB08

1. Fault content

Engine cooling system: There is no emergency operation signal on the coolant pump.

2. Fault Cause Analysis

This fault indicates that the ECU has detected that the water pump communication protocol has not set emergency operation mode, and the function is missing. This fault is recorded.

Reason: The communication protocol of the water pump has not set the function of emergency operation mode.

3. Troubleshooting methods (in order)

A. Check if there is an open circuit or short circuit to the ground wire in the emergency line (adjacent to the positive pole line of the power supply) from the ECU to the water pump. The normal emergency line voltage is basically the same as the power supply (with an error of ± 1V).

B. Check if the water pump harness connector has good contact.

C. Unplug the water pump plug and start the engine. Measure if there is voltage on the emergency wire of the plug. If there is no voltage, check the ECU module. If there is voltage, try replacing the same model of water pump.

The above are the ten common failure modes of BMW electronic water pumps, hoping to be helpful to you. Jianke Electronics specializes in the production of automotive electronic water pumps, with closed-loop control from development, production to sales, and MES system traceability management throughout the entire process from injection molding, SMT to assembly, ensuring stable and reliable product quality, making your choice worry free.