TSBs

Comparing Chevy Sonic injector wires

Feb. 18, 2025

This bulletin applies to 2012-2020 Chevy Sonic vehicles equipped with a 1.4L engine and MH8 6T40 or MZ4 MR5 6-speed manual transmission.

Mike Mavrigian

Related To:

Mitchell 1

While performing a visual inspection, refer to engine control schematics to compare the fuel injection control circuit wire colors at the fuel injectors and at the ECM connections.

This bulletin applies to 2012-2020 Chevy Sonic vehicles equipped with a 1.4L engine and MH8 6T40 or MZ4 MR5 6-speed manual transmission.

You may encounter a rough idle, surge, shudder, poor transmission shift feel and misfire, with or without DTC P0300 set in the ECM.

While performing a visual inspection, refer to engine control schematics to compare the fuel injection control circuit wire colors at the fuel injectors and at the ECM connections.

The connections at the fuel injectors or individual circuits at the ECM connectors can be reversed, leading to misfires that occur only under specific circumstances or RPM ranges, making them difficult to duplicate or diagnose.

About the Author

Mike Mavrigian | Motor Age Editor

Mike Mavrigian has written thousands of automotive technical magazine articles involving a variety of specialties, from engine building to wheel alignment, and has authored more than a dozen books that crisscross the automotive spectrum. Mike operates Birchwood Automotive, an Ohio shop that builds custom engines and performs vintage vehicle restorations. The shop also features a professional photo studio to document projects and to create images for articles and books.