Non-Monitored Circuits

NON-MONITORED CIRCUITS (DIESEL)
The ECM does not directly monitor the following circuits, systems, and conditions even though they could have malfunctions that result in driveability problems. A diagnostic code may not be displayed for the following conditions. However, problems with these systems may cause a diagnostic code to be displayed for other systems.

Engine Timing - The ECM can detect incorrectly indexed timing gears; however, cannot detect improper valve adjustment.

Fuel Inlet Restriction - On a CARB certified vehicle, the ECM can detect a clogged fuel pump inlet filter, clogged in-tank filter, or a pinched supply line. On an EPA certified vehicle, the ECM cannot detect a clogged fuel pump inlet filter, clogged in-tank filter, or a pinched supply line.

Fuel Injectors - On a CARB certified vehicle, the ECM can detect if a fuel injector is clogged, or if the pintle is sticking. On an EPA certified vehicle, the ECM cannot detect if a fuel injector is clogged, or if the pintle is sticking.

Fuel Requirements - Poor quality or air in fuel can cause problems such as hard starting, no starting, stalling, and stumble.

PCM Grounds - The PCM and ECM cannot detect a poor system ground. However, a diagnostic trouble code may be stored as a result of this condition.

Air Cleaner Air Flow - The PCM and ECM cannot detect a clogged or restricted air cleaner inlet or filter element, however, this condition may lead to a low power/hard start type of complaint.

Exhaust System - The PCM and ECM cannot detect a plugged, restricted, or leaking exhaust system, however, this condition may lead to a low power/hard start type of complaint.

The PCM does not monitor the following circuits, Systems, and conditions even though they could have malfunctions that result in driveability problems. A diagnostic code may not be displayed for the following conditions. However, problems with these systems may cause a diagnostic code to be displayed for other systems. For example, a fuel pressure problem will not register a diagnostic code directly, but could cause a rich or lean condition. This could cause an oxygen sensor, fuel system, or misfire monitor trouble code to be stored in the PCM.