AutoCodes – GMC – U1842 GMC

U1842 GMC Code - Lost Communication With ECM/PCM

Quick Answer

The system voltage is between 9-16 volts. Common causes include Faulty Engine Control Module (ECM)/Powertrain Control Module (PCM), Engine Control Module /Powertrain Control Module harness is open or shorted, Engine Control Module /Powertrain Control Module 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: U1842 GMC indicates Lost Communication With ECM/PCM.
Common causes: Common causes include Faulty Engine Control Module (ECM)/Powertrain Control Module (PCM), Engine Control Module /Powertrain Control Module harness is open or shorted, Engine Control Module /Powertrain Control Module 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 580

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 Jun 08, 2020

Description
Possible Causes
How To Fix
Cost to Diagnose
FAQs
Comments
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Code U1842 GMC Description

The system voltage is between 9-16 volts. The vehicle power mode master indicates that the need for serial data communications. The Diagnostic Trouble Code (DTC) will set when a supervised periodic message that includes the transmitter device availability has not been received.

OBDII Code U1842 GMC - Lost Communication With ECM/PCM - AutoCodes.com — U1842 GMC Code - Lost Communication With ECM/PCM

What does this mean?

What are the Possible Causes of the DTC U1842 GMC?

Faulty Engine Control Module (ECM)/Powertrain Control Module (PCM)
Engine Control Module /Powertrain Control Module harness is open or shorted
Engine Control Module /Powertrain Control Module circuit poor electrical connection

How to Fix the DTC U1842 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 U1842 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.

Need more information about the U1842 GMC code?

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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 U1842 GMC Code

1. What are the common symptoms of OBDII code U1842 GMC?

- Common symptoms include issues with starting the vehicle, engine stalling, poor performance, or the vehicle going into limp mode.

2. What are the possible causes of the U1842 GMC code?

- The code may be triggered by a faulty ECM/PCM, damaged wiring or connectors, a loose connection, or a communication bus issue.

3. How can I diagnose the U1842 GMC code?

- Diagnosis involves checking the wiring and connectors for damage, ensuring proper connections, testing the ECM/PCM, and using a scan tool to monitor communication data.

4. Can a DIYer repair the U1842 GMC code?

- While some basic checks like inspecting connections can be done by DIYers, diagnosing and repairing communication issues with the ECM/PCM may require professional help.

5. What are some repair tips for resolving the U1842 GMC code?

- Repair tips include checking for loose connections, repairing or replacing damaged wiring, ensuring proper grounding, and reprogramming or replacing the ECM/PCM if necessary.

6. Is it safe to drive with the U1842 GMC code present?

- It is not recommended to drive with this code active, as it can lead to potential safety hazards and further damage to the vehicle.

7. Can the U1842 GMC code be intermittent?

- Yes, the code may sometimes appear intermittently due to loose connections or temporary communication issues, making diagnosis more challenging.

8. How long does it typically take to fix the U1842 GMC code?

- The time to fix the code can vary depending on the cause and complexity of the issue, ranging from a quick connector repair to a more involved ECM/PCM replacement.

9. Will resetting the trouble codes make the U1842 GMC code disappear?

- Resetting the codes may temporarily clear the U1842 GMC code, but it is crucial to diagnose and address the underlying issue to prevent it from reoccurring.

10. Can extreme weather conditions trigger the U1842 GMC code?

- Yes, extreme weather conditions such as extreme heat or cold can sometimes affect the communication systems in the vehicle, potentially leading to the U1842 GMC code.