Non-Monitored Circuits

NOTE: The following circuits, systems and conditions that cause driveability problems are not monitored by the Powertrain Control Module (PCM). Fault codes may not be displayed for these areas, but problems with them may cause fault codes to be displayed for other systems. For example, a fuel injector problem will not yield a fault directly, but could cause a rich or lean fuel mixture condition. This could cause an oxygen sensor fault to be stored in the PCM.

NON-MONITORED CIRCUITS
Cylinder Compression - The PCM cannot detect uneven, high, or low engine cylinder compression.

PCM Connector Engagement - The PCM cannot tell if connector pins are spread or damaged, but a fault code may be set as a result of this condition.

PCM System Ground - The PCM has no way of determining a poor system ground, but a fault may be generated if a poor system ground condition exists.

Engine Timing - The PCM cannot tell if a cam gear, crank gear, or ignition distributor is indexed incorrectly. Any of the previous problems could result in a lean or rich air/fuel mixture, causing an oxygen sensor fault to be generated.

Evaporative System - The PCM has no way to determine if the charcoal canister or its purge hoses are plugged, restricted, or loaded with fuel.

Excessive Oil Consumption - Even though the PCM monitors exhaust oxygen content, via the oxygen sensor, when the vehicle is in closed loop, it cannot detect excessive oil consumption.

Exhaust System - The PCM cannot determine or detect if an exhaust system is plugged, restricted, or leaking.

Fuel Pressure - Fuel pressure is controlled by the pressure regulator, and the pressure regulator is controlled by the vacuum signal sent from the throttle body. The PCM cannot determine if the fuel pump pressure is too low or high, if the fuel filter is clogged, if the inlet or return lines are pinched or restricted, or if the fuel pump filter is clogged or restricted. Any of the previous problems could cause a lean or rich air/fuel mixture, resulting in an oxygen sensor code being generated.

Fuel Injector Malfunctions - The PCM cannot determine if the wrong injector has been installed, if the pintle is clogged or stuck, or if the injector tip has completely worn out. Any of the previous problems could cause a lean or rich air/fuel mixture, resulting in an oxygen sensor code being generated.

Secondary Ignition Circuit - The PCM cannot detect fouled or worn spark plugs, inoperative ignition coil, ignition cross firing, or open spark plug cables.

Throttle Body Air Flow - The PCM cannot detect a clogged air filter element, a restricted air cleaner inlet, a dirty throttle body or plenum, or a clogged or dirty air bypass passage. Any of the previous problems could cause a lean or rich air/fuel mixture, resulting in an oxygen sensor code being generated.

Vacuum Assist - The PCM cannot determine if the vacuum circuits of the vacuum assisted components have leaks, restrictions, or cracked hoses. Any of the previous problems could cause a MAP sensor fault to be generated.