American Style: Working with a paper clip
GM cars from before 1993 have an OBD, an on-board diagnostic connection. To use that cunning device you naturally need tools, 'tools' as you wish. "Apps". After all, are we talking about electronics?
Incidentally, such an ODB was devised by California for environmental reasons
So what you need is a paper clip.
The connector is located to the left of the steering column under the dashboard and has 12 holes. Pierce the legs of the paper clip in the upper, right holes. Switch the ignition on and the controller or the 'check engine' light flashes. Count the flashes between breaks. Each code consists of two numbers and the number 12 always comes first to show that the on-board computer does not receive any information that tells it that the car is working. The engine is off. The computer repeats its report twice before continuing to search.
Then you can for example see "Flash, Flash, Flash - PAUSE, Flash". That is 31 code. Each code is 'flashed' three times before the next diagnosis is made.
When all reports have been made, the paper clip can be returned to the desk and the contact can be turned off.
Repair the reported defects and then reset the computer by disconnecting the - 5 battery cable from its pole for minutes.
We give the notifications as they appear in the shop manual:
code - code definition
12 diagnostic mode
13 - 02 sensor or circuit
14 coolant sensor or circuit / high temp indicated
15 coolant sensor or circuit / low temp indicated
16 system voltage out of range
19 crankshaft position sensor or circuit
21 throttle position sensor or circuit voltage high
22 throttle position sensor or circuit voltage low
23 mixture control (m / c) solenoid or circuit (carbureted models)
23 manifold air temperature (mat) sensor or circuit (1990 and earlier models) 23 intake air temperature (iat) sensor circuit (fuel-injected models)
24 vehicle speed sensor (vss) or circuit
25 - manifold air temperature (mat) sensor or circuit - high temperature indicated (1990 and earlier models)
25 - intake air temperature (iat) sensor or circuit - high temperature indicated (1991 and later models)
26 quad driver module circuit
27 quad driver module circuit
28 quad driver module circuit
29 quad driver module circuit
31 park / neutral position (pnp) switch circuit
32 baro sensor or circuit (carbureted models)
32-egr circuit (fuel-injected models)
33 manifold absolute pressure (map sensor signal voltage high
33 - mass air flow (maf) sensor or circuit - excessive airflow indicated
34 manifold absolute pressure (map) sensor signal voltage low
34 - mass air flow (maf) sensor signal - low airflow indicated
35 idle speed control (isc) switch or circuit (shorted) (carbureted models)
35 idle air control (iac) valve / circuit
38 brake switch circuit
39- torque converter clutch (tcc) circuit
41- no distributor signals to ecm, or faulty ignition module (carbed models)
41 cylinders select error mem-cal or ecm problem (fuel-injected models
41-cam sensor circuit (3.8 engine)
42 bypass or electronic spark timing (est) circuit
43 - low voltage at terminal I (carbureted models)
43 knock sensor circuit
44 oxygen sensor or circuit - lean exhaust detected
45 oxygen sensor or circuit - rich exhaust detected
46-power steering pressure switch circuit
48 misfire diagnosis
51 prom, mem-cal or ecm problem
52 calpak or ecm problem
53-egr fault (carbureted models only)
53 system over-voltage (ecm over 17.7 volts)
54 mixture control (m / c) solenoid or circuit (carbureted models)
54 fuel pump circuit (1986 and later models)
55 oxygen sensor circuit or ecm
55 fuel lean monitor (2.2l engine)
61 oxygen sensor signal faulty (possible contaminated sensor)
62 transaxle gear switch signal circuits
63- manifold absolute pressure (map) sensor voltage high (low vacuum detected)
64- manifold absolute pressure (map) sensor voltage low (high vacuum detected)
66 pressure sensor or circuit air conditioning
Handy?
Yes. The estimate of a defective machine was - very much in budget terms - read as a failure due to only 1 broken spark plug cable ...