The engine computer tracks current flow during the glow plug heating phase. If the current draw on cylinder 4 is mismatching the other cylinders, this code triggers. This occurs when the plug has degraded or you install an incorrect replacement part. Always replace plugs with matching resistance specs to prevent feedback errors.
Mechanic Glossary
4 Glow Plug Incorrect
A fault indicating that current draw or resistance from the cylinder 4 glow plug is outside standard limits.
Frequently Asked Questions
The engine computer detected abnormal current draw from cylinder 4 glow plug during the pre-heat cycle.
No. They have completely different resistance ratings. Mixing them will trigger an incorrect code and can damage the controller.
Verify the plug part number matches the other cylinders, and replace it if it is the wrong spec or has failed.