Non-Monitored Circuits

The PCM does not monitor following circuits, systems, and conditions even though they could have malfunctions that result in driveability problems. A diagnostic code may not be displayed for 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 PCM.

NOTE: Any of these conditions marked with (*) could result in a rich or lean condition causing an oxygen sensor trouble code to be stored in PCM, or vehicle may exhibit one or more driveability symptoms listed in table of contents.

Engine Timing (*) - The PCM cannot detect an incorrectly indexed timing chain, camshaft sprocket, or crankshaft sprocket. The PCM also cannot detect an incorrectly indexed distributor.

Fuel Pressure (*) - Fuel pressure is controlled by fuel pressure regulator. The PCM cannot detect a clogged fuel pump inlet filter, clogged in-line filter, or a pinched fuel supply.

Fuel Injectors (*) - The PCM cannot detect if a fuel injector is clogged, pintle is sticking, or wrong injectors are installed.

Fuel Requirements - Poor quality gasoline can cause problems such as hard starting, stalling, and stumble. Use of methanol-gasoline blends may result in starting and driveability problems.

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

Throttle Body Air Flow (*) - The PCM cannot detect a clogged or restricted air cleaner inlet or filter element.

Exhaust System (*) - The PCM cannot detect a plugged, restricted, or leaking exhaust system.

Cylinder Compression (*) - The PCM cannot detect uneven, low, or high engine cylinder compression.

Excessive Oil Consumption - Although PCM monitors exhaust stream oxygen content through oxygen sensor when system is in a closed loop, it cannot determine excessive oil consumption.