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

Engine Timing - The engine controller cannot detect an incorrectly indexed timing chain, camshaft sprocket and crankshaft sprocket. However, these could result in a rich or lean condition causing an oxygen sensor fault to be stored in the engine controller.

Cylinder Compression - The engine controller cannot detect uneven, low, or high engine cylinder compression.

Exhaust System - The engine controller cannot detect a plugged, restricted or leaking exhaust system.

Fuel Injector Malfunctions - The engine controller cannot determine if a fuel injector is clogged, the needle is sticking or the wrong injector is installed. However, these could result in a rich or lean condition causing an oxygen sensor fault to be stored in the engine controller.

Excessive Oil Consumption - Although the engine controller monitors exhaust stream oxygen content when the system is in closed loop, it cannot determine excessive oil consumption.

Throttle Body Air Flow - The engine controller cannot detect a clogged or restricted air cleaner inlet or filter element.

Evaporative System - The engine controller will not detect a restricted, plugged or loaded evaporative purge canister.

Vacuum Assist - Leaks or restrictions in the vacuum circuits of vacuum assisted engine control system devices are not monitored by the engine controller. However, these could result in a MAP sensor fault being stored in the engine controller.

Engine Controller System Ground - The engine controller cannot determine a poor system ground. However, a fault code may be generated as a result of this condition.

Engine Controller Connector Engagement - The engine controller cannot determine spread or damaged connector pins. However, a fault code may be generated as a result of this condition.

HIGH AND LOW LIMITS

The engine controller compares input signal voltages from each input device with established high and low limits for the device. If the input voltage is not within limits and other fault code criteria are met, a fault code will be stored in memory. Other fault code criteria might include engine RPM limits or input voltages from other sensors or switches that must be present before a fault condition can be verified.

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FAULT CODE DESCRIPTION

A fault code indicates that the engine controller has recognized an abnormal condition in the system. Fault codes can be obtained from the Check Engine lamp on the Instrument Panel or from the Diagnostic Readout Box II (DRBII). Fault codes indicate the results of a failure but do not identify the failed component directly.

SYSTEM TESTS

WARNING: APPLY PARKING BRAKE AND/OR BLOCK WHEELS BEFORE PERFORMING ANY TEST ON AN OPERATING ENGINE.

OBTAINING FAULT CODES

(1)Connect DRBII to the diagnostic connector located in the engine compartment near the driver side strut tower (Fig. 15).

(2)Start the engine if possible, cycle the transmission selector and the A/C switch if applicable. Shut off the engine.

(3)Turn the ignition switch on, access Read Fault Screen. Record all the fault messages shown on the DRBII. Observe the check engine lamp on the instrument panel. The lamp should light for 2 seconds then go out (bulb check).

Fault code erasure; access erase fault code data

STATE DISPLAY TEST MODE

The switch inputs used by the engine controller have only two recognized states, HIGH and LOW. For this reason, the engine controller cannot recognize the difference between a selected switch position versus an open circuit, a short circuit, or a defective switch. If the change is displayed, it can be assumed that the entire switch circuit to the engine controller is functional. From the state display screen access either State Display Inputs and Outputs or State Display Sensors.

STATE DISPLAY INPUTS AND OUTPUTS

Connect the DRB II tester to the vehicle and access the State Display screen. Then access Inputs and Outputs. The following is a list of the engine control system functions accessible through the Inputs and Outputs screen.

Park/Neutral Switch

Speed Control Resume Brake Switch

Speed Control On/Off Speed Control Set A/C Switch Sense

Z2 Voltage Sense

S/C Vent Solenoid S/C Vacuum Solenoid