AutoCodes – Generic – P1A89

P1A89 Code - 42 Volt System Voltage Low

Quick Answer

The Accessory Power Module (APM) supplies the energy that flows between the high voltage, 300 volt, direct current (DC) and intermediate voltage, 42 volt, DC to support the Electric Power Steering (EPS). Common causes include Faulty Accessory Power Module (APM), Accessory Power Module (APM) harness is open or shorted, Accessory Power Module (APM) 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: P1A89 indicates 42 Volt System Voltage Low.
Common causes: Common causes include Faulty Accessory Power Module (APM), Accessory Power Module (APM) harness is open or shorted, Accessory Power Module (APM) 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 2,952

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 Feb 23, 2020

Description
Possible Causes
How To Fix
Cost to Diagnose
FAQs
Comments
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Code P1A89 Description

The Accessory Power Module (APM) supplies the energy that flows between the high voltage, 300 volt, direct current (DC) and intermediate voltage, 42 volt, DC to support the Electric Power Steering (EPS). The APM receives a 42 volt enable command from the Hybrid Powertrain Control Module (HPCM) over the high speed hybrid GMLAN communication circuit. 42 volt APM functions will run only when the 42 volt APM enable is active on the high speed hybrid GMLAN communication circuit.

OBDII Code P1A89 - 42 Volt System Voltage Low - AutoCodes.com — P1A89 Code - 42 Volt System Voltage Low

What does this mean?

What are the Possible Causes of the DTC P1A89?

Faulty Accessory Power Module (APM)
Accessory Power Module (APM) harness is open or shorted
Accessory Power Module (APM) circuit poor electrical connection

How to Fix the DTC P1A89?

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 P1A89 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 P1A89 code?

Need more information on how to fix the P1A89 code? Get Access to Factory Service Manuals

Need Help with the Code?

Get the P1A89 code diagnosed by a professional: Find a repair shop in your area

Information for Specific Makes

P1A89 Buick — 42 Volt System Voltage Low
P1A89 Cadillac — 42 Volt System Voltage Low
P1A89 Chevrolet — 42 Volt System Voltage Low
P1A89 GMC — 42 Volt System Voltage Low
P1A89 Saturn — 42 Volt System Voltage Low

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 P1A89 Code

1. What are the common symptoms of OBDII code P1A89 (42 Volt System Voltage Low)?

- Common symptoms include dimming headlights, difficulty starting the vehicle, and issues with the electrical system.

2. What are the possible causes of OBDII code P1A89 (42 Volt System Voltage Low)?

- Causes may include a faulty battery, failing alternator, loose or corroded connections, or issues with the voltage regulator.

3. How can I diagnose the 42 Volt System Voltage Low code?

- You can diagnose the code by checking the battery voltage with a multimeter, inspecting the alternator and its connections, and testing the voltage regulator.

4. What are the repair tips for resolving OBDII code P1A89?

- Repair tips may include replacing the battery if it is old or faulty, repairing or replacing the alternator, cleaning and tightening electrical connections, and checking the voltage regulator.

5. Is it safe to continue driving with OBDII code P1A89 (42 Volt System Voltage Low)?

- It is not recommended to continue driving with this code as it can lead to further electrical issues and potential vehicle breakdowns.

6. Can a DIY enthusiast fix OBDII code P1A89 (42 Volt System Voltage Low)?

- Depending on the root cause, some DIY enthusiasts with automotive experience and the right tools may be able to address the issue by following repair guides and instructions.

7. How much does it typically cost to repair OBDII code P1A89?

- Repair costs can vary depending on the cause of the issue, but it may involve expenses related to battery replacement, alternator repair or replacement, and labor charges.

8. Will resetting the OBDII code P1A89 resolve the issue temporarily?

- Resetting the code may temporarily clear the warning light, but if the underlying issue causing the low voltage is not addressed, the problem is likely to recur.

9. How urgent is it to address OBDII code P1A89 (42 Volt System Voltage Low)?

- It is recommended to address this code promptly to prevent further damage to the vehicle's electrical system and ensure safe operation.

10. Can extreme weather conditions contribute to triggering OBDII code P1A89?

- Yes, extreme weather conditions, especially cold temperatures, can put additional strain on the battery and alternator, potentially leading to low voltage issues.