Is your 1g throwing a check engine light? Here is a simple way to diagnose it without the use of a scantool or diagnostic checker.
All you will need is a simple voltmeter. First, locate the OBD (Is right next to the fuse box near the driver's feet).
Take off the black cover. Turn the ignition to "ON" to turn the electrical on. Wait 5 seconds until connecting the pos/neg voltmeter terminals. Connect the positive wire of the voltmeter to pin 1 (upper left pin) and the negative to pin 12 (lower right pin). Here is a pin layout of the port.
The needle on the voltmeter should make a series of "sweeps". It should consist of a certain number of long sweeps followed by a number of short sweeps. Make sure you watch what the needle does. For example, one long sweep followed by three quick sweeps equals "13". Then, you take that code and look up what code that is diagnosing. Here is the list:
For 90-92 turbos:
1. ECU
11. Oxygen sensor
12. Air flow sensor (Maf)
13. Intake air temp sensor
14. TPS
21. Engine coolant temp sensor
22. Crank angle sensor
23. TDC sensor (cylinders 1 and 4)
24. Vehicle speed sensor
25. Barometric pressure sensor
31. Detonation sensor (knock sensor)
41. Injector(s)
42. Fuel pump
43. EGR
44. Ignition coil
9. Normal state
For 93-94 turbos:
1. ECU
11. Heated oxygen sensor
12. Volume air flow sensor (Maf)
13. Intake air temp sensor
14. TPS
21. Engine coolant temp sensor
22. Crankshaft position sensor
23. Camshaft position sensor
24. Vehicle speed sensor
25. Barometric pressure sensor
31. Detonation sensor (knock sensor)
41. Injector(s)
42. Fuel pump
43. EGR
44. Ignition coil or transistor
9. Normal state
NOTE/EDIT: This can also be done with a digital voltmeter. A short sweep is going to be less than 1v while a long sweep will be around 14v.
Keep in mind that this can be done with nonturbos. I specifically posted towards 1g turbos because I don't have non turbo codes.
Feel free to email me with comments or questions.
Thanks, Jim
