What does P1823 mean on a Chevy?

P1823. Internal Mode Switch P Circuit Low Voltage. Applies to Impala, Malibu, Monte Carlo, Silverado, Sierra.

What causes P1823 on a Chevy?

Faulty internal mode switch inside the transmission Short to ground in IMS signal P parity circuit Misadjusted shift cable holding the switch between detents Internal transmission harness shorted to ground Corroded AT inline connector

How do I fix P1823 on a Chevy?

Observe IMS A/B/C/P parameters in each shifter detent with a Tech2 scan tool Verify shift cable adjustment before opening the transmission Test IMS signal P circuit for a short to ground Inspect the internal harness and AT inline connector Replace the internal mode switch if circuits and adjustment test normal

Code

P1823

Internal Mode Switch P Circuit Low Voltage

Category: Powertrain - Transmission
Severity: Check Engine Light
Applies to: Impala, Malibu, Monte Carlo, Silverado, Sierra
Related: No single generic twin. See OBD Codes List

What it means

P1823. Internal Mode Switch P Circuit Low Voltage. This Chevy-enhanced code applies to Impala, Malibu, Monte Carlo, Silverado, Sierra.

Findings, check these first

Faulty internal mode switch inside the transmission
Short to ground in IMS signal P parity circuit
Misadjusted shift cable holding the switch between detents
Internal transmission harness shorted to ground
Corroded AT inline connector

Standard procedure

Observe IMS A/B/C/P parameters in each shifter detent with a Tech2 scan tool
Verify shift cable adjustment before opening the transmission
Test IMS signal P circuit for a short to ground
Inspect the internal harness and AT inline connector
Replace the internal mode switch if circuits and adjustment test normal

Look up another code

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Sources and review

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Last updated 2026-09-13.

Report a correction for P1823. Include your vehicle, the issue and a source if you have one.