The P0691: Fan 1 Control Circuit Low code indicates that the control module has detected low voltage in the control circuit for Fan 1. This issue can affect the cooling system, leading to potential overheating of the engine. The low voltage could be due to a faulty fan, wiring problems, or a malfunction in the control circuit.
P0691 – Quick Overview
Code | Information |
---|---|
Meaning | P0691: Fan 1 Control Circuit Low |
Is it serious? | Yes, as it can lead to engine overheating if the fan does not operate correctly. |
Possible causes | – Low voltage in Fan 1 control circuit – Faulty fan – Wiring issue |
How to diagnose? | – Test fan 1 control circuit for voltage – Inspect wiring and connectors – Replace fan if necessary |
P0691 Meaning
The P0691 code means that the control module has detected lower-than-expected voltage in the control circuit for Fan 1. This low voltage condition may prevent the fan from operating, which can result in engine overheating, particularly under heavy load or in hot weather conditions.
Step-by-step diagnostic guide
Action | Description | Tools Needed |
---|---|---|
Check for Other Codes | Use an OBD-II scanner to check for additional related codes, particularly those affecting the cooling system or fan control. | OBD-II Scanner |
Test the Fan 1 Control Circuit for Voltage | Use a multimeter to measure the voltage in the control circuit for Fan 1. Ensure that the voltage meets the manufacturer’s specifications. | Multimeter |
Inspect Wiring and Connectors | Inspect the wiring and connectors leading to Fan 1 for signs of damage, corrosion, or loose connections that could result in low voltage. | Flashlight, Multimeter |
Test the Fan for Functionality | Test Fan 1 to ensure it is functioning correctly and not causing the low voltage condition. Replace the fan if it is faulty. | Diagnostic Tool, Multimeter |
Replace the Fan if Necessary | If the fan is found to be faulty, replace it to ensure proper cooling of the engine and prevent overheating. | Replacement Fan, Tools |
Clear the Code and Test | After repairs, clear the code using an OBD-II scanner and test the vehicle to ensure Fan 1 is functioning correctly and that the code does not return. | OBD-II Scanner, Vehicle Manual |

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