GM Buick Cadillac Chevy GMC Oldsmobile Pontiac Trouble Codes
Most gm cars made before 1995 are equipped with the ODB1 computer operating system.
This system is unique to the GM manufactured cars and truck which Include: Buick,
Cadillac, Chevy, GMC, Oldsmobile and Pontiac. To start diagnostic trouble code gathering
locate the ALDL (assembly line data link) connector which is located on the driver’s
side lower part of the dash on most cases. In this connector are two terminals that
need to be connected with a wire jumper. Once the wire is inserted into the connector
turn the ignition key to
the "on" position without starting the engine. The
check engine light will start to flash, count the flashes this will be the first
digit of the two number code, example for code 14, one flash, pause, then, four
light flashes. There will be a pause in the check engine light the first code flashing series
has concluded and the second number flash is about to begin. Once the second set
of flashing has stopped the end of trouble codes
is finished. If there is more than one code stored in the
computer the first
digit of the second code will begin. If there are no additional trouble codes the
light will continue to flash the original code and code 12 which tells you there
are no more codes stored until the key is turned off or the jumper wire removed.
Code 12 is normal to sometimes flash first two or three times before the actual
trouble code is displayed.
Use a jumper wire and connect terminals A and B on the ALDL.
GM Trouble Codes for OBD1 Computer Operating System12 - System normal13 - oxygen sensor circuit open14 - coolant sensor high resistance or shorted15 - coolant sensor circuit low or open16 - direct ignition system (DIS) fault in circuit
17 - cam position sensor fault18 - crank or cam sensor error19 - crank sensor circuit fault21 - tps sensor out of range22 - tps sensor signal voltage low23 - intake air temp sensor out of range, low
24 - vehicle speed (vss) sensor circuit fault25 - air temp sensor sensor out of range, high26 - quad-driver module (computer) circuit #1 fault27 - quad-driver module (computer) 2nd gear circuit28 - quad-driver module (computer) circuit #2 fault29 - quad driver module (computer) 4th gear circuit31 - cam position sensor fault32 - egr circuit fault33 - map sensor signal out of range, high34 - map sensor signal out of range, low35 - idle air control sensor circuit fault36 - ignition system circuit error38 - brake input circuit fault39 - clutch input circuit fault41 - cam sensor circuit fault, ignition control circuit fault42 - electronic spark timing (EST) circuit grounded43 - knock sensor or electronic spark control circuit fault44 - oxygen sensor lean exhaust45 - oxygen sensor rich exhaust46 - pass-key II circuit or power steering pressure switch circuit fault47 - pcm-bcm data circuit48 - misfire diagnosis51 - calibration error, mem-cal, ecm or eprom failure52 - engine oil temperature circuit, low temperature indicated53 - battery voltage error or egr or pass-key II circuit54 - egr system failure or fuel pump circuit low voltage55 - a/d converter error or pcm not grounded or lean fuel or founded reference voltage56 - quad-driver module #2 circuit57 - boost control problem58 - vehicle anti-theft system fuel enable circuit61 - a/c system performance or degraded oxygen sensor signal62 - engine oil temperature high temperature indicated63 - oxygen sensor right side circuit open or map sensor out of range64 - oxygen sensor right side lean exhaust indicated65 - oxygen sensor right side rich exhaust indicated66 a/c pressure sensor circuit low pressure67 - a/c pressure sensor circuit or a/c clutch circuit failure68 - a/c compressor relay circuit failure69 - a/c clutch circuit head pressure high70 - a/c refrigerant pressure circuit high71 - a/c evaporator temperature sensor circuit low72 - gear selector switch circuit73 - a/c evaporator temperature circuit high75 - digital egr #1 solenoid error76 - digital egr #2 solenoid error77 - digital egr #3 solenoid error79 - vehicle speed sensor (vss) circuit signal high80 - vehicle speed sensor (vss) circuit signal low81 - brake input circuit fault82 - ignition control (IC) 3X signal error85 - prom error86 - analog/digital pcm error87 - eprom error99 - power managementRelated Car Repair InformationIf further assistance is needed, our certified car repair technicians are ready to answer your car questions.
Diagnostic Connector
GM Trouble Codes for OBD1 Computer Operating System12 - System normal13 - oxygen sensor circuit open14 - coolant sensor high resistance or shorted15 - coolant sensor circuit low or open16 - direct ignition system (DIS) fault in circuit
17 - cam position sensor fault18 - crank or cam sensor error19 - crank sensor circuit fault21 - tps sensor out of range22 - tps sensor signal voltage low23 - intake air temp sensor out of range, low
24 - vehicle speed (vss) sensor circuit fault25 - air temp sensor sensor out of range, high26 - quad-driver module (computer) circuit #1 fault27 - quad-driver module (computer) 2nd gear circuit28 - quad-driver module (computer) circuit #2 fault29 - quad driver module (computer) 4th gear circuit31 - cam position sensor fault32 - egr circuit fault33 - map sensor signal out of range, high34 - map sensor signal out of range, low35 - idle air control sensor circuit fault36 - ignition system circuit error38 - brake input circuit fault39 - clutch input circuit fault41 - cam sensor circuit fault, ignition control circuit fault42 - electronic spark timing (EST) circuit grounded43 - knock sensor or electronic spark control circuit fault44 - oxygen sensor lean exhaust45 - oxygen sensor rich exhaust46 - pass-key II circuit or power steering pressure switch circuit fault47 - pcm-bcm data circuit48 - misfire diagnosis51 - calibration error, mem-cal, ecm or eprom failure52 - engine oil temperature circuit, low temperature indicated53 - battery voltage error or egr or pass-key II circuit54 - egr system failure or fuel pump circuit low voltage55 - a/d converter error or pcm not grounded or lean fuel or founded reference voltage56 - quad-driver module #2 circuit57 - boost control problem58 - vehicle anti-theft system fuel enable circuit61 - a/c system performance or degraded oxygen sensor signal62 - engine oil temperature high temperature indicated63 - oxygen sensor right side circuit open or map sensor out of range64 - oxygen sensor right side lean exhaust indicated65 - oxygen sensor right side rich exhaust indicated66 a/c pressure sensor circuit low pressure67 - a/c pressure sensor circuit or a/c clutch circuit failure68 - a/c compressor relay circuit failure69 - a/c clutch circuit head pressure high70 - a/c refrigerant pressure circuit high71 - a/c evaporator temperature sensor circuit low72 - gear selector switch circuit73 - a/c evaporator temperature circuit high75 - digital egr #1 solenoid error76 - digital egr #2 solenoid error77 - digital egr #3 solenoid error79 - vehicle speed sensor (vss) circuit signal high80 - vehicle speed sensor (vss) circuit signal low81 - brake input circuit fault82 - ignition control (IC) 3X signal error85 - prom error86 - analog/digital pcm error87 - eprom error99 - power managementRelated Car Repair InformationIf further assistance is needed, our certified car repair technicians are ready to answer your car questions.