Файл: 92FWD_14.pdf

(31) Verify engine ground strap is attached at the engine and dash panel (Figs. 24 and 25).

Fig. 24 Engine Ground Strap at Intake Manifold

Fig. 25 Engine Ground Strap to Dash Panel

(32) Verify oxygen sensor electrical connector is attached to the sensor (Fig. 26).

Fig. 26 Heated Oxygen Sensor Electrical

Connection

(33) Check Hose and Wiring Connections at Fuel Pump. Check that wiring connector is making contact with terminals on pump.

ON BOARD DIAGNOSTICS

The engine controller has been programmed to monitor many different circuits of the fuel injection system. If a problem is sensed with a monitored circuit often enough to indicate an actual problem, the controller stores a fault. If the problem is repaired or ceases to exist, the controller cancels the Fault Code after 50 to 100 vehicle key on/off cycles.

Certain criteria must be met for a fault code to be entered into engine controller memory. The criteria may be a specific range of engine RPM, engine temperature, and/or input voltage to the engine controller.

It is possible that a fault code for a monitored circuit may not be entered into memory even though a malfunction has occurred. This may happen because one of the fault code criteria for the circuit has not been met. For example, assume that one of the fault code criteria for the MAP sensor circuit is that the engine must be operating between 750 and 2000 RPM to be monitored for a fault code. If the MAP sensor output circuit shorts to ground when engine RPM is above 2400 RPM (resulting in a 0 volt input to the engine controller) a fault code will not be entered into memory. This is because the condition does not occur within the specified RPM range.

There are several operating conditions that the engine controller does not monitor and set fault codes for. Refer to Monitored Circuits and Non-Monitored Circuits in this section.

Stored fault codes can be displayed by cycling the ignition key On - Off - On - Off - On. Also, the technician can display fault information using the Diagnostic Readout Box II (DRB II). The DRB II connects to the diagnostic connector in the vehicle (Fig. 27, 28 or 29).

MONITORED CIRCUITS

The engine controller can detect certain fault conditions in the fuel injection system.

Open or Shorted Circuit - The engine controller can determine if the sensor output (input to controller) is within proper range, and if the circuit is open or shorted.

Output Device Current Flow - The engine controller senses whether the output devices are hooked up. If there is a problem with the circuit, the controller senses whether the circuit is open, shorted to ground, or shorted high.

Oxygen Sensor - The engine controller can determine if the oxygen sensor is switching between rich and lean once the system has entered closed loop. Refer to Modes of Operation in this section for an explanation of closed loop operation.

Fig. 27 Diagnostic Connector LocationÐAA and AP

Vehicles

Fig. 28 Diagnostic Connector LocationÐAC Ve-

hicles

Fig. 29 Diagnostic Connector LocationÐAG and AJ

Vehicles

NON-MONITORED CIRCUITS

The engine controller does not monitor the following circuits, systems and conditions that could have malfunctions that result in driveability problems. Fault codes may not be displayed for these conditions. However, problems with these systems may cause fault codes to be displayed for other systems. For example, a fuel pressure problem will not register a fault directly, but could cause a rich or lean condition. This could cause an oxygen sensor fault to be stored in the engine controller.

Fuel Pressure - Fuel pressure is controlled by the fuel pressure regulator. The engine controller cannot detect a clogged fuel pump inlet filter, clogged in-line fuel filter, or a pinched fuel supply or return line. However, these could result in a rich or lean condition causing an oxygen sensor fault.

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. The engine controller also cannot detect an incorrectly indexed distributor. 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 the fuel injector is clogged, the pintle 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 the exhaust stream oxygen content through the oxygen sensor 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.

Ä

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

FUEL SYSTEMS 14 - 35

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

Vehicle Speed

Oxygen Sensor State

MAP Gauge Reading

Throttle Opening

Total Spark Advance

CIRCUIT ACTUATION TEST MODE

The circuit actuation test mode checks for proper operation of output circuits or devices which the engine controller cannot internally recognize. The engine controller can attempt to activate these outputs and allow an observer to verify proper operation. Most of the tests provide an audible or visual indication of device operation (click of relay contacts, spray fuel, etc.). With the exception of an intermittent condition, if a device functions properly during its test, it can be assumed that the device, its associated wiring, and its driver circuit are in working order.

OBTAINING CIRCUIT ACTUATION TEST

Connect the DRB II tester to the vehicle and access the Actuators screen. The following is a list of the engine control system functions accessible through Actuators screens.

Stop All Tests

Ignition Coil #1

Fuel Injector #1

AIS Motor Open/Close Radiator Fan Relay A/C Clutch Relay Auto Shutdown Relay Purge Solenoid

S/C Servo Solenoids Alternator Field Tachometer Output

PTU Solenoid (Automatic Only) EGR Solenoid

All Solenoids/Relays

ASD Fuel System Test

THROTTLE BODY MINIMUM AIR FLOW CHECK PROCEDURE

(1)Connect Diagnostic Readout Box II (DRBII).

(2)Remove air cleaner assembly. Plug the heated air door vacuum hose.

(3)Warm engine in Park or Neutral until the cooling fan has cycled on and off at least once.

(4)Hook-up timing check device and tachometer.

(5)Disconnect the coolant temperature sensor and set basic timing to 12°BTDC 6 2°BTDC.

(6)Shut off engine. Reconnect coolant temperature sensor.

(7)Disconnect the PCV valve hose from the intake manifold nipple.

(8)Attach Air Metering Fitting #6457 (Fig. 30) to the intake manifold PCV nipple.

(9)Restart the engine, allow engine to idle for at least one minute.

Fig. 30 Air Metering Fitting

(10)Using the DRBII, Access Min Airflow Idle Spd in the sensor read test mode.

(11)The following will then occur:

²AIS motor will fully close.

²Idle spark advance will become fixed.

²Idle fuel will be provided at a set value.

²Engine RPM will be displayed on Diagnostic Readout Box II (DRBII).

(12)Check idle RPM with tachometer. If idle RPM is within the specifications listed below, then the throttle body minimum air flow is set correctly.

IDLE SPECIFICATIONS

If idle RPM is not within specification replace throttle body.

(13)Shut off engine.

(14)Remove Special Tool number 6457 from intake manifold PCV nipple. Reinstall the PCV valve hose.

(15)Remove DRBII.

(16)Reinstall air cleaner assembly. Reinstall heated air door vacuum hose.

(17)Disconnect timing check device and tachom-

eter.

IGNITION TIMING PROCEDURE

Refer to Group 8D Ignition System

60-WAY ENGINE CONTROLLER WIRING CONNECTOR

Refer to the engine controller wiring connector descriptions (Fig. 31) for information regarding wire colors and cavity numbers.