AutoCodes – GMC – P1641 GMC

P1641 GMC Code - Cooling Fan Relay 1 Control Circuit

Quick Answer

Ignition voltage is supplied to the Cooling Fan relay coil. Common causes include Faulty Cooling Fan Relay, Cooling Fan Relay harness is open or shorted, Cooling Fan Relay circuit poor electrical component. Severity is High - diagnose this code as soon as possible. Driving is not recommended if the warning light is flashing, the engine runs poorly, or safety-related symptoms are present.

What it means
P1641 GMC indicates Cooling Fan Relay 1 Control Circuit.
Common causes
Common causes include Faulty Cooling Fan Relay, Cooling Fan Relay harness is open or shorted, Cooling Fan Relay circuit poor electrical component.
Severity
High - diagnose this code as soon as possible.
Can I drive?
Driving is not recommended if the warning light is flashing, the engine runs poorly, or safety-related symptoms are present.
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Code Popularity 4,823
How popular is this code, among other codes? Low
Table of contents Created and updated by William Orellana on Sep 04, 2019
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Code P1641 GMC Description

Ignition voltage is supplied to the Cooling Fan relay coil. The Powertrain Control Module (PCM) controls the relay by grounding the control circuit via an internal switch called a driver. The primary function of the driver is to supply the ground for the component being controlled. Each driver has a fault line which is monitored by the PCM. When the PCM is commanding a component ON, the voltage of the control circuit should be low (near 0 volts). When the PCM is commanding the control circuit to a component OFF, the voltage potential of the circuit should be high (near battery voltage). If the fault detection circuit senses a voltage other than what is expected, the fault line status will change causing the code to set.
The relay is used to control the high current flow to the cooling fan motors. This allows the PCM driver to only have to handle the relatively low current used by the relay.
OBDII Code P1641 GMC - Cooling Fan Relay 1 Control Circuit - AutoCodes.com
P1641 GMC Code - Cooling Fan Relay 1 Control Circuit

What are the Possible Causes of the DTC P1641 GMC?

  • Faulty Cooling Fan Relay
  • Cooling Fan Relay harness is open or shorted
  • Cooling Fan Relay circuit poor electrical component

How to Fix the DTC P1641 GMC?

Review the 'Possible Causes' above and visually examine the corresponding wiring harness and connectors. Check for damaged components and inspect connector pins for signs of being broken, bent, pushed out, or corroded.

What is the Cost to Diagnose the Code?

Labor: 1.0

To diagnose the P1641 GMC code, it typically requires 1.0 hour of labor. Rates vary by location, vehicle, and shop. Many shops charge between $80–$150 per hour; dealerships and metro areas may be higher, independents may be lower.

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About the author: William Orellana is a Master Mechanic and Mechanical Engineer with over 30 years of experience diagnosing and repairing vehicles. Learn more about his background.

Frequently Asked Questions about P1641 GMC Code

What does OBDII code P1641 mean for a GMC vehicle?

P1641 indicates an issue with the Cooling Fan Relay 1 Control Circuit, which can affect the operation of the cooling fans.

What are the common symptoms of code P1641 in GMC vehicles?

Symptoms may include engine overheating, cooling fans not activating, or the check engine light being illuminated.

What causes code P1641 on GMC vehicles?

Possible causes include a faulty cooling fan relay, damaged wiring or connectors, or issues with the powertrain control module (PCM).

How do I diagnose code P1641 on my GMC?

Start by inspecting the cooling fan relay, wiring, and connectors for damage or corrosion. Use a multimeter to test the relay and circuit continuity.

Can a bad cooling fan relay cause code P1641?

Yes, a malfunctioning cooling fan relay is one of the primary causes of this code.

Is it safe to drive with code P1641 on my GMC?

Driving is not recommended if the cooling fans are not functioning, as this can lead to engine overheating and potential damage.

How do you fix code P1641 on a GMC vehicle?

Repairs may involve replacing the cooling fan relay, repairing damaged wiring, or addressing PCM-related issues if necessary.

How much does it cost to fix code P1641 on a GMC?

Repair costs can vary, but replacing a cooling fan relay typically costs $50-$150, while wiring repairs or PCM issues may be more expensive.

Can code P1641 be caused by a software issue in the PCM?

Yes, a software glitch or failure in the PCM can sometimes be responsible for this code.

Will clearing the code P1641 without repairs solve the problem?

Clearing the code without addressing the underlying issue may temporarily turn off the check engine light, but the problem will likely return.

Discuss the causes and fixes for P1641 GMC OBDII Code

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