AutoCodes – GMC – P1823 GMC

P1823 GMC Code - Internal Mode Switch Circuit 'P' Low

Quick Answer

With the engine runtime over 5 seconds, system voltage from 8-18v, Fuel Cutoff inactive, engine torque from 30-148 ft-lb (40-200 Nm), the Powertrain Control Module (PCM) received an Internal Mode Switch (IMS) signal indicating PARK for 2 seconds, and then the IMS indicated a transitional state between Neutral and D4, conditions met for 5 seconds. Common causes include Faulty Internal Mode Switch, Internal Mode Switch harness is open or shorted, Internal Mode Switch 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: P1823 GMC indicates Internal Mode Switch Circuit 'P' Low.
Common causes: Common causes include Faulty Internal Mode Switch, Internal Mode Switch harness is open or shorted, Internal Mode Switch 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 1,336

How popular is this code, among other codes? Low

Repair Importance Level

Urgent (Diagnose now) (3 / 3)

Repair Difficulty Level

Advanced (Pro) (3 / 3)

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Table of contents Created and updated by William Orellana on Sep 21, 2019

Description
Possible Causes
How To Fix
Cost to Diagnose
FAQs
Comments
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Code P1823 GMC Description

OBDII Code P1823 GMC - Internal Mode Switch Circuit 'P' Low - AutoCodes.com — P1823 GMC Code - Internal Mode Switch Circuit 'P' Low

What does this mean?

What are the Possible Causes of the DTC P1823 GMC?

Faulty Internal Mode Switch
Internal Mode Switch harness is open or shorted
Internal Mode Switch circuit poor electrical connection

How to Fix the DTC P1823 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 P1823 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.

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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 P1823 GMC Code

1. What does the OBDII code P1823 mean on a GMC vehicle?

P1823 indicates a problem with the Internal Mode Switch (IMS) Circuit 'P,' which is responsible for monitoring the transmission gear position. A "low" signal suggests an electrical issue in the circuit.

2. What are the common symptoms of the P1823 code in a GMC?

Symptoms may include the transmission stuck in a single gear (limp mode), erratic shifting, illumination of the check engine light, or incorrect gear display on the dashboard.

3. What causes the P1823 code to appear in a GMC?

Common causes include a faulty Internal Mode Switch (IMS), damaged or corroded wiring and connectors, a malfunctioning transmission control module (TCM), or low transmission fluid.

4. Can driving with the P1823 code damage my GMC vehicle?

Yes, continued driving with this code may lead to further transmission issues, reduced performance, and potential damage to internal components over time.

5. How do I diagnose the P1823 code on my GMC?

Start by scanning the vehicle with an OBDII tool to confirm the code, then inspect the IMS, wiring, and connectors for damage or corrosion. Testing the IMS and related circuits with a multimeter can help pinpoint the issue.

6. How is the P1823 code fixed on a GMC vehicle?

Repairs may involve replacing the Internal Mode Switch, repairing damaged wiring or connectors, cleaning corroded connections, or reprogramming the TCM if necessary.

7. How much does it cost to fix the P1823 code on a GMC?

Repair costs vary but typically range from $150 to $500, depending on whether the IMS needs replacement or if wiring repairs are required.

8. Can low transmission fluid cause the P1823 code on a GMC?

Yes, low or contaminated transmission fluid can cause improper IMS operation, leading to the P1823 code. Always check and maintain proper fluid levels.

9. Is the P1823 code specific to GMC vehicles?

While P1823 is more common in GMC and General Motors vehicles, it may also appear in other makes with similar transmission systems.

10. Can a bad transmission control module (TCM) trigger the P1823 code?

Yes, a malfunctioning TCM can send incorrect signals to the IMS, causing the P1823 code to appear. However, TCM failure is less common than wiring or IMS issues.