AutoCodes – Pontiac – P1642 Pontiac

P1642 Pontiac 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 Pontiac 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 3,807

How popular is this code, among other codes? Low

Repair Importance Level

Urgent (Diagnose now) (3 / 3)

Repair Difficulty Level

Advanced (Pro) (3 / 3)

What is this?

Table of contents Created and updated by William Orellana on Sep 04, 2019

Description
Possible Causes
How To Fix
Cost to Diagnose
FAQs
Comments
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Code P1642 Pontiac 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 Pontiac - Fan Control Relay 2 and 3 Control Circuit - AutoCodes.com — P1642 Pontiac Code - Fan Control Relay 2 and 3 Control Circuit

What does this mean?

What are the Possible Causes of the DTC P1642 Pontiac?

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 Pontiac?

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 Pontiac 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 P1642 Pontiac Code

What does the OBDII code P1642 mean for a Pontiac vehicle?

1. P1642 indicates a problem with the Fan Control Relay 2 and 3 Control Circuit, which manages the operation of the cooling fans in the engine. 2.

What are the common symptoms of code P1642 in a Pontiac?

Symptoms may include the cooling fans not operating properly, engine overheating, the check engine light turning on, or reduced air conditioning efficiency. 3.

What causes the P1642 code to appear?

Common causes include a faulty fan control relay, damaged wiring or connectors in the control circuit, a blown fuse, or a malfunctioning powertrain control module (PCM). 4.

Can I drive my Pontiac with a P1642 code?

Driving with a P1642 code is not recommended, as improper fan operation can lead to engine overheating, which can cause severe engine damage. 5.

How can I diagnose the P1642 code on my Pontiac?

Start by inspecting the fan control relays, wiring, and connectors for damage, corrosion, or loose connections. Use a multimeter to test the relay and verify proper circuit function. 6.

What repairs can fix the P1642 code?

Repairs may include replacing a faulty fan control relay, repairing or replacing damaged wiring or connectors, replacing a blown fuse, or reprogramming or replacing the PCM if necessary. 7.

How much does it cost to fix a P1642 code?

Repair costs vary depending on the issue but could range from $50 for a simple relay replacement to $500 or more if the PCM needs to be replaced or reprogrammed. 8.

Can a bad thermostat cause the P1642 code?

While a bad thermostat can contribute to cooling system issues, it is not a direct cause of the P1642 code, which specifically relates to the fan control circuit. 9.

Is the P1642 code specific to Pontiac vehicles?

No, the P1642 code can appear in other vehicles as well, but the exact diagnosis and repair steps may vary depending on the make and model. 10.

How do I prevent the P1642 code from recurring?

Regularly inspect and maintain the cooling system, ensuring that relays, wiring, and connectors remain in good condition and free of corrosion or damage.