AutoCodes – Generic – P2B85

P2B85 Code - Engine Coolant Pump Underspeed

Quick Answer

The cooling system's function is to maintain an efficient engine operating temperature during all engine speeds and operating conditions. Common causes include Faulty Engine Coolant Pump, Engine Coolant Pump harness is open or shorted, Engine Coolant Pump circuit poor electrical connection. 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: P2B85 indicates Engine Coolant Pump Underspeed.
Common causes: Common causes include Faulty Engine Coolant Pump, Engine Coolant Pump harness is open or shorted, Engine Coolant Pump circuit poor electrical connection.
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 3,108

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 Aug 19, 2022

Description
Possible Causes
How To Fix
Cost to Diagnose
FAQs
Comments
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Code P2B85 Description

The cooling system's function is to maintain an efficient engine operating temperature during all engine speeds and operating conditions. The cooling system is designed to remove various amounts of the heat produced by the burning of the air-fuel mixture. When the engine is cold, the coolant does not flow to the radiator until the thermostat opens. This allows the engine to warm up quickly. The Diagnostic Trouble Code (DTC) will be set when the Engine Coolant Pump Speed, both desired and actual are not within a calibrated range for greater than 10 s.

OBDII Code P2B85 - Engine Coolant Pump Underspeed - AutoCodes.com — P2B85 Code - Engine Coolant Pump Underspeed

What does this mean?

What are the Possible Causes of the DTC P2B85?

Faulty Engine Coolant Pump
Engine Coolant Pump harness is open or shorted
Engine Coolant Pump circuit poor electrical connection
Faulty Engine Control Module (ECM)

How to Fix the DTC P2B85?

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 P2B85 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 P2B85 code?

Need more information on how to fix the P2B85 code? Get Access to Factory Service Manuals

Need Help with the Code?

Get the P2B85 code diagnosed by a professional: Find a repair shop in your area

Information for Specific Makes

P2B85 Buick — Engine Coolant Pump Underspeed
P2B85 Cadillac — Engine Coolant Pump Underspeed
P2B85 Chevrolet — Engine Coolant Pump Underspeed
P2B85 GMC — Engine Coolant Pump Underspeed

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 P2B85 Code

What does the OBDII code P2B85 mean?

The P2B85 code indicates an "Engine Coolant Pump Underspeed," meaning the coolant pump is not operating at the expected speed, which can affect engine cooling.

What are the common symptoms of code P2B85?

Symptoms may include engine overheating, reduced engine performance, illumination of the check engine light, or unusual noises from the coolant pump.

What causes the P2B85 code to appear?

Common causes include a failing or damaged coolant pump, issues with the pump's motor or wiring, a malfunctioning engine control module (ECM), or debris obstructing the pump.

Can I drive with the P2B85 code active?

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

How do I diagnose the P2B85 code?

Diagnosis involves checking the coolant pump for physical damage, testing the electrical connections and wiring, and using a scan tool to monitor pump speed and related parameters.

Is the P2B85 code related to low coolant levels?

While low coolant levels can cause engine overheating, the P2B85 code specifically refers to the coolant pump's underspeed, which is typically a mechanical or electrical issue.

How do I fix the P2B85 code?

Repairs may include replacing the coolant pump if it's faulty, repairing damaged wiring or connectors, or addressing ECM-related issues that affect pump speed control.

Can a clogged cooling system trigger the P2B85 code?

Yes, a clogged cooling system can restrict coolant flow, potentially causing the pump to work inefficiently and trigger the underspeed code.

How much does it cost to repair the P2B85 code?

The repair cost varies, but replacing a coolant pump can range from $300 to $700, depending on the vehicle make and model, plus any additional diagnostic or labor fees.

Does the P2B85 code require reprogramming the ECM?

In some cases, if the ECM is not properly controlling the coolant pump speed, reprogramming or updating the ECM software may be necessary.