P23E1: EGR C Control Circuit/Open

P23E1 covers the electrical drive of EGR valve C, a third exhaust gas recirculation actuator next to valves A and B. Which valve carries the letter C is up to the manufacturer; no carmaker documents P23E1 publicly. The code means the module has found the control circuit open or otherwise faulty. GM's 2018 diesel tables show how the A-side equivalent P0403 works: with the H-bridge driver off and the valve commanded away from closed, a load resistance above 200 kΩ in 96 of 120 samples sets the code as Type B, MIL after two trips. A similar check is plausible for valve C. CARB requires EGR components to be monitored for circuit faults. With this path disabled, NOx rises. Shorts are P23E3 and P23E4.

Medium severity. Can I keep driving?You can normally drive in moderation, but get it repaired soon: if the valve is stuck open, the engine may idle very poorly.

Symptoms

Warning lamp with otherwise normal driving
Raised NOx at emissions testing

Most likely causes

Unplugged or corroded connector at EGR valve C
Open motor winding or solenoid coil in valve C
Broken drive wire between engine module and valve C

What to check, in order

Start with the simplest. You can tick off each step.

Check the connector and any vacuum hoses
Check the continuity of the wire between the component and the control module.
Use live data to compare the commanded opening with the actual opening
Clean the valve and passages if they are clogged with carbon
Test the actuator with the scanner
Replace the valve if it still does not follow the command after cleaning

Good to know

Repair difficulty: medium
It affects emissions.

What each character of P23E1 means

P: Powertrain: engine and transmission
2: Generic code: same on every make
3: Ignition and misfires
E1: Specific fault in that system

Frequently asked questions

Can I keep driving with code P23E1?

You can normally drive in moderation, but get it repaired soon: if the valve is stuck open, the engine may idle very poorly.

What causes code P23E1?

The most common causes are: unplugged or corroded connector at EGR valve C; open motor winding or solenoid coil in valve C; broken drive wire between engine module and valve C.

Related codes

Sources

Values and procedures vary by manufacturer. If it affects brakes, steering, fuel or high voltage, see a professional. Updated: 2026-11-04. How we build these pages.