Fix P0691: STEP-BY-STEP diagnostic GUIDE!

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

CodeInformation
MeaningP0691: 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

ActionDescriptionTools Needed
Check for Other CodesUse 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 VoltageUse 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 ConnectorsInspect 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 FunctionalityTest 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 NecessaryIf 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 TestAfter 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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