How to Scan a Check Engine Light on a Pre-1996 Chevy/GMC Without a Scan Tool (Plus Full Codes List!)

GM OBD 1 Codes List:
12 No Engine Speed Sensor Reference Pulse To PCM/TCM
13 Open Oxygen Sensor Circuit
14 CTS Voltage Low (Sensor Or Signal Line Grounded)
15 CTS Voltage High (Sensor, Connections, Or Wires Open)
21 TPS Voltage High (Open Circuit Or Misadjusted TPS)
22 TPS Voltage Low (Circuit Grounded)
23 Intake Air Temperature Sensor Voltage High
24 Vehicle Speed Sensor Circuit Open Or Grounded
25 Intake Air Temperature Sensor Voltage Low
28 Pressure Switch Manifold Range Circuit Open Or Shorted
31 Turbocharger Wastegate Overboost
32 EGR Error (Improper Vacuum Signal)
33 MAP Voltage High (Circuit Open Or Short To Voltage)
34 MAP Voltage Low (Circuit Open Or Short To Ground)
35 IAC System Fault
39 TCC Stuck Off (Faulty TCC Solenoid)
42 EST Circuit Fault
43 ESC Fault
44 Lean Exhaust Indicated
45 Rich Exhaust Indicated
51 Improperly Installed/Faulty PROM/MEM-CAL
52 Fuel CAL-PAC Missing
53 System Voltage High (Charging System Problem)
54 Fuel Pump Circuit Voltage Low
55 Faulty ECM
58 TTS High Temperature (Sensor Or Signal Line Grounded)
59 TTS Low Temperature (Sensor, Connections, Or Wires Open)
68 Overdrive Ratio Error (Engine RPM Greater Than Input Speed)
73 Force Motor Commanded Amperage Differs From Return
75 System Voltage Low (Charging System Problem)
81 QDM Solenoid "B" Monitored Voltage Differs From Commanded
82 QDM Solenoid "A" Monitored Voltage Differs From Commanded
83 QDM TCC Monitored Voltage Differs From Commanded
85 Undefined Gear Ratio (Input Or Output Sensor Failure)
86 Shift Solenoid "B" Stuck On (Commanded Gear Not Engaged)
87 Shift Solenoid "B" Stuck Off (Commanded Gear Not Engaged)

[@oneobserver6116]

Brought back memories of me doing this to the '84 Monte Carlo I used to own many years ago. I would then get out my trusty Haynes Repair Manual and look up the codes.😊

[@Techie_ASMR]

great video

[@freespirit1975]

Jack, I have a 1995 Ford Thunderbird LX with a 4.6L engine. I have a CEL lit up, not to mention an air bag light blinking for a looong time (I counted the blinks on that airbag light so at least I know what that problem is-front sensor problem and steering wheel sensor problem-probably the bags are just old). But for the CEL, I purchased an OBD II reader and it didn't fit the socket-wrong shape and number of pins. So I purchased an ODBI reader and it didn't fit either! I did some reading and it appears that car was somehow caught in purgatory between the OBDI and OBDII transition when it was manufactured, and I assumed that Ford dealerships had the reader to read the codes because they did work on it back in the day (I've owned it since new). I also heard from one local Ford dealer that they probably threw away all that stuff long ago. It's an old car but in very good condition and I'd like to know what the code is so I can fix it before the bulb burns out. Have you heard of this problem and do you have any advice? I have the official Ford Shop Manuals for this car so I have all of the codes. I have read that you can count the needle deflections on an analog multimeter to get the code number. If so how would I do that? I read somwhere in the past you could do that but I have forgotten how. I still have an old analog meter. Maybe I could try the paperclip trick but as I said, I apparently don't have an OBDI system.

[@donniev8181]

Can this be done on other makes? My uncle has a obd1 jeep and is having a small issue.