Checking the codes on a 89-91
All you need is a piece of wire, your car key, and the list of codes below.
Right beside the battery and the coil there should be a single green plug. Stick one end of the wire in there. Now ground the other end to the battery "-" or the frame. now stick the key in the ign. and turn it to "on" (not start!!). if you have codes stored, the check engine light should turn off for a few secs. then will come on and start flashing. if it's on for more then a sec. then that is a count of 10. If it is flashing fast that is a one. for examble the code #31 would be "---- ---- ---- -" then it will stop for a few secs, and repeat it (asuming only one code is stored) If more then one code is pressent, it will show the lowest # first. and display the rest in order.
(89 turbo
shown)
here is what the #'s mean, taken from a '90 fatory workshop manual. should be the same for 89-91
* turbo only
~ non turbo only
| Code# | Input Device | malfunction | Fail-safe function |
| 01 | trailing ignition coil | malfunction of spark plug, broken wire, short circuit | Trailing side ignitions pulse cut |
| 02 | crank angle sensor (ne sensor) | broken wire, short circuit | fuel injection and ignition cut |
| 03 | crank angle sensor (g sensor) | broken wire, short circuit | fuel injection and ignition cut |
| 05* | knock sensor | Broken wire, short circuit | Ignition timming retarded |
| 08 | airflow meter (AFM) | broken wire, short circuit | basic fuel injection amount and fixed timing |
| 09 | water thermosensor | broken wire, short circuit | coolant temp fixed at 80 degrees C (176F) |
| 10 | intake air thermosensor (AFM) | broken wire, short circuit | intake air temp fixed at 20C (68F) |
| 11 | intake air thermosensor (engine) | broken wire, short circuit | intake air temp fixed at 20C (68F) |
| 12 | Throttle sensor (full range) | broken wire, short circuit | throttle valve opening angle signal fixed at 20% |
| 13 | pressure sensor (intake manifold) | broken wire, short circuit | intake pressure fixed at 760 mmHg (29.9 inhg) |
| 14 | atmospheric pressure sensor | malfunctioning ECU | at. Pressure fixed at 760 mmHg |
| 15 | oxygen sensor | oxygen sensor output remains below 0.55v 80 sec. after F/B system operation beginning | feedback system canceled(for EGI) |
| 17 | feedback system | oxygen sensor output remains 0.55v 10 sec. after F/B system operation beginning | feedback system canceled(for EGI) |
| 18 | throttle sensor (narrow range) | broken wire, short circuit | signal fixed at full open |
| 20 | metering oil pump position sensor | broken wire, short circuit | Mop fixed smallest open. basic fuel amount and timing fixed |
| 27 | metering oil pump (MOP) | malfunctioning MOP, step motors, broken wire, short circuit, or malfunctioning ECU | Mop fixed smallest open,basic fuel amount and timing fixed |
| 37 | metering oil pump (MOP) | malfunctioning MOP, step motors, broken wire, short circuit, or malfunctioning ECU | basic fuel amount and timing fixed |
| Code # | Output device |
| 25 | solenoid valve (pressure regulator control (PRC)) |
| 26 | step motor (MOP) |
| 30 | split air solenoid valve |
| 31 | solenoid valve (relief) |
| 32 | solenoid valve (switch) |
| 33 | port air solenoid valve |
| 34 | solenoid valve (bypass air control (bac)) |
| 38 | solenoid valve (accelerated warm-up system) |
| 40~ | auxiliary port valve |
| 41~ | solenoid valve (variable dynamic effect intake control (vdi)) |
| 42* | Duty solenoid (turbo boost pressure control) |
| 51 | fuel pump resistor relay |
| 71 | injector (front secondary) |
| 73 | injector (rear secondary) |
after you get the codes out and fix the problem (or even before) you have to reset the ECU to get rid of them.
Just disconnect the Neg battery terminal for more then 5 secs. If the codes come back then you didn't fix the problem.