What does P1661 mean on a Chevy?

P1661. Malfunction indicator lamp control circuit fault. Check engine light circuit has failed. Applies to Silverado, Sierra, S10, Blazer 1998 to 2004..

What causes P1661 on a Chevy?

Burned out MIL bulb Open in MIL control wire Short in MIL circuit Faulty instrument cluster Faulty powertrain control module driver

How do I fix P1661 on a Chevy?

Check if MIL lights at key on Inspect cluster bulb and wiring Test MIL control circuit Check cluster operation Replace faulty cluster or module driver

Code

P1661

Malfunction indicator lamp control circuit fault

Category: Powertrain - Computer and Auxiliary Controls
Severity: Check Engine Light
Applies to: Silverado, Sierra, S10, Blazer 1998 to 2004.
Related: No single generic twin. See OBD Codes List

What it means

P1661. Malfunction indicator lamp control circuit fault. Check engine light circuit has failed. This Chevy-enhanced code applies to Silverado, Sierra, S10, Blazer 1998 to 2004..

Findings, check these first

Burned out MIL bulb
Open in MIL control wire
Short in MIL circuit
Faulty instrument cluster
Faulty powertrain control module driver

Standard procedure

Check if MIL lights at key on
Inspect cluster bulb and wiring
Test MIL control circuit
Check cluster operation
Replace faulty cluster or module driver

Look up another code

Press / to jump to the box. Chevy-enhanced powertrain, body, chassis and network codes.

Sources and review

Review: checked against the recorded source material.

OBDII Code P1661 CHEVROLET - MIL Control Circuit | Engine-Codes.com
archived reference page (engine-codes.com via Wayback Machine)
Supports: code identity and Chevrolet application
Fetched directly. MIL control circuit matches the catalog malfunction indicator lamp control circuit. Model and year fitment remain curator claims.

Last updated 2026-09-25.

Report a correction for P1661. Include your vehicle, the issue and a source if you have one.