AutoCodes – GMC – P1338 GMC

P1338 GMC Code - Cylinder 1 Glow Plug Offset Exceeded Learning Limit

Quick Answer

The Glow Plug Control Module has not learned the glow plug offset values. Common causes include Perform Glow Plug Learn procedure, Faulty Glow Plug 1, Glow Plug 1 harness is open or shorted. 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: P1338 GMC indicates Cylinder 1 Glow Plug Offset Exceeded Learning Limit.
Common causes: Common causes include Perform Glow Plug Learn procedure, Faulty Glow Plug 1, Glow Plug 1 harness is open or shorted.
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 3,458

How popular is this code, among other codes? Low

Repair Importance Level

Urgent (Diagnose now) (3 / 3)

Repair Difficulty Level

Intermediate (2 / 3)

What is this?

Table of contents Created and updated by William Orellana on Sep 30, 2022

Description
Possible Causes
How To Fix
Tech Notes
Cost to Diagnose
FAQs
Comments
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Code P1338 GMC Description

The Glow Plug Control Module has not learned the glow plug offset values. If a glow plug has been replaced and the glow plug learn was not performed, or if the Glow Plug Control Module experiences an Electronically Erasable Programmable Read Only Memory (EEPROM) error or data corruption, this Diagnostic Trouble Code (DTC) to set. The DTC will be set if the glow plug hot resistance is outside a predefined threshold.

OBDII Code P1338 GMC - Cylinder 1 Glow Plug Offset Exceeded Learning Limit - AutoCodes.com — P1338 GMC Code - Cylinder 1 Glow Plug Offset Exceeded Learning Limit

What does this mean?

What are the Possible Causes of the DTC P1338 GMC?

Perform Glow Plug Learn procedure
Faulty Glow Plug 1
Glow Plug 1 harness is open or shorted
Glow Plug 1 circuit poor electrical connection

How to Fix the DTC P1338 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 does this mean?

Code Tech Notes

If a Glow Plug was replaced, perform a Glow Plug Learn procedure with a Scan Tool.

What is the Cost to Diagnose the Code?

Labor: 1.0

To diagnose the P1338 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 P1338 GMC code?

Need more information on how to fix the P1338 GMC code? Get Access to Factory Service Manuals

Need Help with the Code?

Get the P1338 GMC code diagnosed by a professional: Find a repair shop in your area

Information for Specific GMC Models

P1338 2014 GMC Sierra — Cylinder 1 Glow Plug Offset Exceeded Learning Limit
P1338 2015 GMC Sierra — Cylinder 1 Glow Plug Offset Exceeded Learning Limit
P1338 2016 GMC Sierra — Cylinder 1 Glow Plug Offset Exceeded Learning Limit
P1338 2017 GMC Sierra — Cylinder 1 Glow Plug Offset Exceeded Learning Limit
P1338 2018 GMC Sierra — Cylinder 1 Glow Plug Offset Exceeded Learning Limit

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 P1338 GMC Code

1. What are the common symptoms of OBDII code P1338 GMC?

- Common symptoms include rough idling, loss of power, misfires, and increased fuel consumption.

2. What does the OBDII code P1338 GMC indicate?

- This code indicates that the glow plug offset for cylinder 1 has exceeded the learning limit, causing a potential issue with the glow plug system.

3. What are the possible causes of OBDII code P1338 GMC?

- Possible causes include faulty glow plugs, damaged wiring in the glow plug circuit, a problem with the glow plug control module, or issues with the engine control module.

4. How can I diagnose the cause of OBDII code P1338 GMC?

- A thorough visual inspection of the glow plug system, checking the wiring for any damage, and using a multimeter to test the glow plugs can help diagnose the issue.

5. Can I still drive my vehicle with OBDII code P1338 GMC?

- It is not recommended to drive your vehicle with this code active, as it can lead to further engine damage and worsen the symptoms over time.

6. How can I repair OBDII code P1338 GMC?

- Repair options include replacing faulty glow plugs, repairing damaged wiring, replacing the glow plug control module, or reprogramming the engine control module.

7. Is it possible to reset OBDII code P1338 GMC without repairs?

- While clearing the code may temporarily turn off the check engine light, it is important to address the underlying issue to prevent further damage to the engine.

8. Can a DIY enthusiast fix OBDII code P1338 GMC?

- Depending on the skill level and experience with automotive repairs, a DIY enthusiast may be able to address this code by following repair guides and using the necessary tools.

9. How long does it take to repair OBDII code P1338 GMC?

- The repair time can vary depending on the specific cause of the code, but it typically takes a few hours to a full day to diagnose and fix the issue.

10. Are there any preventive measures to avoid OBDII code P1338 GMC?

- Regular maintenance of the glow plug system, such as checking and replacing glow plugs as needed, can help prevent the occurrence of this code.