The "check engine" light is an indicator for a system that monitors many electronic functions in the system, also called the "malfunction indicator lamp" (MIL). It can come on for any of hundreds of different causes from any of the systems that the computer monitors. Some are very important and can lead to further component or engine damage and some are emissions related not as serious but still a problem and need to be repaired.
Your first step is to have the computer scanned to retrieve the trouble codes that were set when the check engine light came on. Those codes will give you specific information about what the computer saw and will get you pointed in the right direction to find your problem.
Diagnostic Trouble Codes - 1987
12 No Reference Pulse
13 Oxygen Sensor Circuit
14 Coolant Sensor Shorted
15 Coolant Sensor Circuit Open
21 Throttle Position Sensor (TPS) (Signal Voltage High)
22 Throttle Position Sensor (TPS) (Signal Voltage Low)
23 Mixture Control (M/C) Solenoid Voltage Low
24 Vehicle Speed Sensor (VSS) Circuit
32 BARO Sensor Voltage Low
34 Differential Pressure (VAC) Sensor - Voltage Incorrect
41 No Distributor Reference Signal
42 Electronic Spark Timing (EST) or Bypass Fault
43 Electronic Spark Control (ESC) Voltage Low to ECM
44 Oxygen Sensor Circuit (Lean Exhaust Indication)
45 Oxygen Sensor Circuit (Rich Exhaust Indicated)
51 PROM Error
53 Exhaust Gas Recirculation (EGR) Control Error
54 Mixture Control Solenoid (M/C) Voltage High
To extract a trouble from the computer for diagnostic purposes, the Assembly Line Communication Link (ALDL) connector is used.
Ground terminals A and B with the ignition "ON" and engine not running. The system will enter the diagnostic mode. In this mode, the computer will display a 12, three consecutive times, by flashing the "CHECK ENGINE", "SERVICE ENGINE SOON" or "MALFUNCTION INDICATOR LAMP" or light. A 12 consists of one flash, a short pause, then two flashes in rapid succession.
After 12 is displayed, any stored trouble s will be displayed by flashing the "CHECK ENGINE", "SERVICE ENGINE SOON" or "MALFUNCTION INDICATOR LAMP" light. All s are displayed 3 times each then a 12 will repeat. In the diagnostic mode, the computer will also energize all computer controlled relays and solenoids.
ALDL Connector (Located Underdash)
Saturday, January 1st, 2011 AT 12:19 AM