What are the common causes of P038B?

A short to ground on the ignition I control wire. A failing ignition coil on the I circuit. A chafed ignition I harness. A weak driver in the ignition module or ECM. Corrosion at the ignition I connector.

Test the ignition I control wire for a short to ground. Swap a known good coil onto the I circuit. Inspect the ignition I harness for chafing. Compare the I control signal to a good cylinder. Replace the coil or module if the control wire tests good. Clear the code and retest.

P038B

Ignition I Control Signal Circuit Low

System: Ignition and misfire (P code)
Lamp: Check Engine Light
Category: Powertrain - Ignition

What it means

P038B means Ignition I Control Signal Circuit Low.

Check these first

A short to ground on the ignition I control wire
A failing ignition coil on the I circuit
A chafed ignition I harness
A weak driver in the ignition module or ECM
Corrosion at the ignition I connector

What to do next

Test the ignition I control wire for a short to ground
Swap a known good coil onto the I circuit
Inspect the ignition I harness for chafing
Compare the I control signal to a good cylinder
Replace the coil or module if the control wire tests good
Clear the code and retest

Look up another code

Code or symptom

Enter a full code or a symptom. Press / to search. How to read a code

Type a code above, or start from a symptom or a common code.

Updated

Generic SAE J2012 definition. Last updated 2026-10-10.