Diagnostic Trouble Code Descriptions

Input signals for sensors, injector and fuel pump are monitored by the computer (ECU). On California models, EGR is also, monitored. The computer stores improper operating conditions of these components in its memory, which can be accessed, using a voltmeter. The malfunction is stored in the computer's memory by power supplied directly from the battery, therefore cannot be erased by turning the ignition key Off. However, if the battery or ECU electrical connector is disconnected, then memory will be erased.
On 4-89.6/1.5L and 4-97.4/1.6L engines less turbocharger, there are 13 malfunction codes plus one for a normal reading that can be stored in memory. On 4-97.4/1.6L turbo engines, there are 14 malfunction codes plus one for a normal reading that can be stored in memory. The codes are as follows:
Code 11-Oxygen Sensor
Code 12-Air Flow Sensor (AFS)
Code 13-Intake Air Temperature Sensor
Code 14-Throttle Position Sensor
Code 15-Motor Position Sensor
Code 21-Engine Coolant Temperature Sensor
Code 22-Crank Angle Sensor
Code 23-TDC Sensor
Code 24-Vehicle Speed Sensor (Reed Switch)
Code 25-Barometric Pressure Sensor
Code 31-Detonation sensor (4-97.4/1.6L Turbo)
Code 41-Injector
Code 42-Fuel Pump
Code 43-EGR (Calif.)
Code 44-Ignition Coil (1989 4-97.4/1.6L)


1988 MPI System Testing

1. Turn ignition to Lock position, then remove ECU cover and disconnect ECU electrical connectors.
2. Set check switch on ECI checker to Off, then the select switch to ``A.''
3. Connect white color connectors labeled ``Checker,'' of harness connector to connectors of ECI checker. Connect harness connector to ECU and harness connector.
4. Perform checks as shown in diagnostic check chart.
5. Turn ignition switch to Lock, then set check switch of ECI checker to Off.
6. Disconnect white color connectors labeled ``Checker,'' of harness connector from ECI checker. Connect green color harness connectors with harness connector labeled ``Checker'' of ECI checker.
7. Perform checks as shown in diagnostic check chart.
8. If checker shows any deviation from specifications, check corresponding sensor and related wiring for defects and repair as necessary.
9. Set check switch of ECI checker to off, then disconnect harness and checker connectors. Leave power supply disconnected from ECU for approximately 15 seconds to clear ECU memory.
10. Connect body harness to ECU, then after testing, road test vehicle to ensure system is operating properly.