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P1642 Chevrolet Code - Fan Control Relay 2 and 3 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
P1642 Chevrolet indicates Fan Control Relay 2 and 3 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 12,123
How popular is this code, among other codes? Low
What is this?
Table of contents Created and updated by William Orellana on Sep 04, 2019
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Code P1642 Chevrolet 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 P1642 Chevrolet - Fan Control Relay 2 and 3 Control Circuit - AutoCodes.com
P1642 Chevrolet Code - Fan Control Relay 2 and 3 Control Circuit
What does this mean?

What are the Possible Causes of the DTC P1642 Chevrolet?

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

How to Fix the DTC P1642 Chevrolet?

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 P1642 Chevrolet 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.

Need more information about the P1642 Chevrolet code?

Need more information on how to fix the P1642 Chevrolet code? Get Access to Factory Service Manuals

Need Help with the Code?

Get the P1642 Chevrolet code diagnosed by a professional: Find a repair shop in your area

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 P1642 Chevrolet Code

1. What are the common symptoms of OBDII code P1642 in a Chevrolet related to Fan Control Relay 2 and 3 Control Circuit?

- Common symptoms include overheating of the engine, erratic cooling fan operation, and potential issues with the vehicle's air conditioning system.

2. What are the typical causes of OBDII code P1642 in a Chevrolet indicating an issue with Fan Control Relay 2 and 3 Control Circuit?

- Possible causes may include a faulty cooling fan relay, damaged wiring or connectors, a defective fan motor, or issues with the engine coolant temperature sensor.

3. How can I diagnose OBDII code P1642 in a Chevrolet specifically related to Fan Control Relay 2 and 3 Control Circuit?

- Diagnosis typically involves inspecting the cooling fan relays, testing the fan motors for functionality, checking the wiring for any damage or loose connections, and verifying the operation of the engine coolant temperature sensor.

4. What are the recommended repair tips for addressing OBDII code P1642 in a Chevrolet related to Fan Control Relay 2 and 3 Control Circuit?

- Repair tips may include replacing the faulty cooling fan relay, repairing any damaged wiring or connectors, testing and replacing the fan motor if necessary, and ensuring proper operation of the engine coolant temperature sensor.

5. Can OBDII code P1642 in a Chevrolet indicating an issue with Fan Control Relay 2 and 3 Control Circuit be safely driven with?

- It is generally not recommended to drive the vehicle with this code active, as it can lead to engine overheating and potential damage if the cooling fan system is not functioning properly.

6. Are there any simple checks I can perform myself before seeking professional help for OBDII code P1642 in a Chevrolet related to Fan Control Relay 2 and 3 Control Circuit?

- You can start by visually inspecting the cooling fan relays and fuses, checking for any obvious wiring issues, and ensuring the fan motors spin freely when powered.

7. How urgent is it to address OBDII code P1642 in a Chevrolet indicating an issue with Fan Control Relay 2 and 3 Control Circuit?

- It is important to address this code promptly to prevent potential engine overheating and damage, especially in hot weather or during heavy traffic conditions.

8. Can a DIY enthusiast with basic automotive knowledge repair OBDII code P1642 in a Chevrolet related to Fan Control Relay 2 and 3 Control Circuit?

- Depending on the specific issue, a DIY enthusiast with basic knowledge may be able to address this code by following repair guides and using the necessary tools for testing and replacing components.

9. Is resetting the OBDII system or clearing the code enough to fix OBDII code P1642 in a Chevrolet linked to Fan Control Relay 2 and 3 Control Circuit?

- Simply clearing the code without addressing the underlying issue will not fix the problem. It is essential to diagnose the root cause and perform the necessary repairs to resolve OBDII code P1642.

10. How much can I expect to pay for professional repairs related to OBDII code P1642 in a Chevrolet involving Fan Control Relay 2 and 3 Control Circuit?

- The cost of professional repairs can vary depending on the specific issue, parts needed, and labor rates. It is advisable to obtain quotes from reputable automotive shops for an accurate estimate.

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