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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 that are programmed into it for that device. If the input voltage is not within specifications 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.

FAULT CODE DESCRIPTION

When a fault code appears, it indicates 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.

SYSTEMS TEST

WARNING: APPLY PARKING BRAKE AND/OR BLOCK WHEELS BEFORE PERFORMING A TEST WITH THE ENGINE OPERATING.

OBTAINING FAULT CODES

(1)Connect DRBII to the diagnostic connector located in the engine compartment near the engine controller.

(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 3 seconds then go out (bulb check).

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

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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 (automatic transmission only) Speed Control Resume

Brake Switch

Speed Control On/Off Speed Control Set A/C Switch Sense B1 Voltage Sense

S/C (Speed Control) Vent Solenoid S/C (Speed Control) Vacuum Solenoid PTU Solenoid

A/C Clutch Relay EGR Solenoid

Auto Shutdown Relay

Radiator Fan Relay Purge Solenoid Check Engine Lamp

STATE DISPLAY SENSORS

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

Battery Temp Sensor

Oxygen Sensor Signal

Coolant Temperature

Coolant Temp Sensor Throttle Position Minimum Throttle Battery Voltage MAP Sensor Reading AIS Motor Position Added Adaptive Fuel Adaptive Fuel Factor Barometric Pressure Min Airflow Idl Spd Engine Speed

Fault #1 Key-On Info

Module Spark Advance

Speed Control Target

Fault #2 Key-On Info

Fault #3 Key-On Info

Speed Control Status

Speed Control Switch Voltage Charging System Goal

Theft Alarm Status

Map Sensor Voltage