GM OBD/OBD2 Codes >> G-Series – Sierra – Suburban – Yukon (1994 – 1995)

Model Year Engine identification System
G-Series 6.5L 1994-95 VIN  position 8 = P/Y GM
Sierra C/K Pickup 6.5L 1994-95 VIN  position 8 = F/P/S GM
Suburban 6.5L 1994-95 VIN  position 8 =  F GM
Yukon  6.5L 1994-95 VIN  position 8 =  S GM

General information

  • Malfunction indicator lamp (MIL) will illuminate if certain faults are recorded .
  • ECM operates in backup mode if sensors fail, to enable vehicle to be driven to repair shop.
  • Trouble codes can be displayed by the MIL or by using a Scan Tool connected to the data link connector (DLC).

Accessing

  • Access data link connector (DLC).
  • Jump data link connector (DLC) terminals A and B [1].
  • Switch ignition ON. 00 NOT start engine.
  • Count MIL flashes. Note trouble codes. Compare with trouble code table.
  • Firstly trouble code 12 will be displayed 3 times.
  • Trouble codes consist of 2 groups, displayed as follows:
o First group indicates the ‘tens’ of the trouble code [2] [A].
o Second group indicates the ‘units’ of the trouble code [2] [C].
o A short pause separates each group [2] [B].
o A long pause separates each trouble code [2] [D].
o For example: Trouble code 12 displayed [2]. Start of diagnosis.
• Each additional trouble code will now be displayed 3 times, in ascending order.
NOTE: If no additional trouble codes are stored, code 12 will continue to be displayed.
• Trouble codes can also be displayed by using a Scan Tool connected to the data link connector (DLC) [1].

Erasing

NOTE: Disconnecting battery ground lead may cause driveability problems until the engine management system relearns basic values.
  • Ensure ignition switched OFF.
  • Disconnect battery ground cable for 30 seconds.
  • Reconnect battery ground cable.
  • Repeat checking procedure to ensure no trouble codes remain in ECM fault memory.
NOTE: Disconnecting battery ground lead may also erase memory from electronic units, such as radio.
  • Trouble codes can also be erased by using a Scan Tool connected to the data link connector (DLC).

Trouble code  identification

Flash code Fault location Probable cause
12 Start of diagnosis No engine speed (RPM) signal received
13 Fuel shut-off solenoid -circuit malfunction Wiring open circuit, fuel shut-oft solenoid, ECM
14 Engine coolant temperature (EeT) sensor voltage low Wiring, ECT sensor, ECM
15 Engine coolant temperature (EeT) sensor voltage high Wiring open circuit, ECT sensor, ECM
16 Vehicle speed sensor (VSS) -no/low signal Wiring, VSS, ECM
17 Injection pump position sensor, high resolution -circuit malfunction Wiring, injection pump position sensor, ECM
18 Injection pump position sensor, low resolution -circuit malfunction Wiring, injection pump position sensor, ECM
19 Crankshaft position (CKP) sensor -circuitmalfunction Wiring, CKP sensor, ECM
21 Accelerator pedal position (APP) sensor 1voltage high Wiring, APP sensor, ECM
22 Accelerator pedal position (APP) sensor 1voltage low Wiring, APP sensor, ECM
23 Accelerator pedal position (APP) sensor 1 to 2/3 -signal variation Wiring, APP sensor, ECM
24 Vehicle speed sensor (VSS) no signal Wiring, VSS, ECM
25 Accelerator pedal position (APP) sensor 2voltage high Wiring, APP sensor, ECM
26 Accelerator pedal position (APP) sensor 2voltage low Wiring, APP sensor, ECM
27 Accelerator pedal position (APP) sensor 2 to 1/3signal variation Wiring, APP sensor, ECM
28 Transmission gear pressure switch, signal -circuit malfunction Wiring open circuit/short circuit to ground,reverse/D1/D2/D3/D4 gear pressure switch(es), ECM
29 Glow plug relay -circuit malfunction Wiring, glow plug relay, ECM
31 Exhaust gas recirculation (EGR) vacuum/ barometric pressure (BARO) sensor -voltage low Wiring, EGR vacuum/BARO sensor, ECM
32 Exhaust gas recirculation (EGR) system -malfunction Wiring, vacuum pipes, EGR vacuum sensor, EGR valve
33 Exhaust gas recirculation (EGR) vacuum/ barometric pressure (BARO) sensor -voltage high Wiring, EGR vacuum/BARO sensor, ECM
34 Fuel injection timing. command/actual -signalvariation Wiring, fuel injection timing actuator, ECM
35 Fuel injection duration -pulse width signal shorter than expected Wiring, fuel injection duration control solenoid, fuel injection pump control module, ECM
36 Fuel injection duration -pulse width signal longer than expected Wiring, fuel injection duration control solenoid, fuel injection pump control module, ECM
37 Brake pedal position (BPP) switch -stuck ON Wiring, BPP switch, ECM
38 Brake pedal position (BPP) switch -stuck OFF Wiring, BPP switch, ECM
39 Brake pedal position (BPP) switch -stuck OFF Wiring, BPP switch, ECM
41 Brake pedal position (BPP) switch. torque converter clutch (TCC) -circuit malfunction Wiring, BPP switch, ECM
42 Fuel temperature sensor -voltage low Wiring, fuel temperature sensor, ECM
43 Fuel temperature sensor -voltage high Wiring, fuel temperature sensor, ECM
44 Exhaust gas recirculation (EGR) valve -circuit malfunction Wiring, fuses, EGR valve
45 Exhaust gas recirculation (EGR) vent valve circuit malfunction Wiring, fuses, EGR vent valve
46 Malfunction indicator lamp (MIL) -circuitmalfunction Wiring, fuses, MIL
47 Intake air temperature (IAT) sensor -voltage low Wiring short circuit to ground, IAT sensor, ECM
48 Intake air temperature (IAT) sensor -voltage high Wiring, IAT sensor, ECM
49 Service throttle soon warning lamp -circuitmalfunction Wiring, fuses, service throttle soon warning lamp
51 Engine control module (ECM). PROM malfunction Poor connections, incorrect programming, ECM
52 System voltage high Alternator, jump started
53 System voltage high Alternator, jump started
54 Engine control module (ECM) malfunction Check trouble code 17, if not: replace ECM
56 Fuel injection pump calibration resistor circuit malfunction Wiring, calibration resistor
57 Engine control module (ECM), sensor supply voltage -circuit malfunction Wiring short to ground, poor connections, MAP sensor
58 Transmission fluid temperature (TFT) sensorvoltage low Wiring short circuit to ground, TFT sensor, ECM
59 Transmission fluid temperature (TFT) sensor voltage high Wiring open circuit, TFT sensor, ECM
61 Turbocharger (TC) boost pressure sensor voltage high Wiring, TC boost pressure sensor, ECM
62 Turbocharger (TC) boost pressure sensor voltage low Wiring short circuit to ground, TC boost pressure sensol”, ECM
63 Accelerator pedal position (APP) sensor 3 voltage high Wiring, APP sensor, ECM
64 Accelerator pedal position (APP) sensor 3 voltage low Wiring, APP sensor, ECM
65 Accelerator pedal position (APP) sensor 3 to 1/2signal variation Wiring, APP sensor, ECM
66 Transmission 3rd-2nd control solenoid -circuit malfunction Wiring, control solenoid, ECM
67 Torque converter clutch (TCC) solenoid -circuit malfunction Wiring, TCC solenoid, ECM
69 Torque converter clutch (TCC) solenoid -stuck ON Wiring open circuit/short circuit to ground, transmission internal wiring, TCC solenoid, transmission mechanical fault, ECM
71 Cruise control , set/coast switch -circuit malfunction Wiring, poor connections, set/coast switch
72 Vehicle speed sensor (VSS) -loss of signal Wiring, V55, ECM
73 Transmission fluid pressure (TFP) control solenoid -circuit malfunction Wiring, poor connection, TFP solenoid
74 Transmission input shaft speed sensor-circuit malfunction Wiring, input shaft speed sensor, ECM
75 System voltage low, engine control module (ECM) Wiring, battery, alternator, ECM
76 Cruise control, resume/acceleration switch -circuit malfunction Wiring, poor connections, resumel acceleration switch
78 Turbocharger (TC) wastegate regulating valve -circuit malfunction Wiring, TC wastegate regulating valve, ECM
79 Transmission fluid temperature (TFT) high Transmission mechanical fault, towing weight limit exceeded
81 Transmission shift solenoid (SS), 2nd-3rd -circuit malfunction Wiring, 55, ECM
82 Transmission shift solenoid (SS), 1st-2nd circuit malfunction . Wiring, SS, ECM
83 Torque converter clutch (TCC) solenoid, pulse width modulated -circuit malfunction Wiring, TCC solenoid, ECM
84 Accelerator pedal position (APP) sensor 1/2/3intermittent circuit malfunction Wiring, poor connections, APP sensor
85 Transmission inpuUoutput shaft speed, ratio variation -out of range Wiring, input shaft speed sensor, output shaft speed sensor, mechanical fault
86 Transmission inpuUoutput shaft speed, ratiovariation -lower than expected Wiring, input shaft speed sensor, output shaft speed sensor, mechanical fault
87 Transmission inpuUoutput shaft speed, ratio variation -higher than expected Wiring, input shaft speed sensor, output shaft speed sensor, mechanical fault
88 Fuel injection pump timing -out of range Fuel injection pump timing incorrectly set
91 Power balance, cylinder 1 Check other trouble codes, if not: mechanical fault
92 Power balance, cylinder 2 Check other trouble codes, if not: mechanical fault
93 Power balance, cylinder 3 Check other trouble codes, if not: mechanical fault
94 Power balance, cylinder 4 Check other trouble codes, if not: mechanical fault
95 Power balance, cylinder 5 Check other trouble codes, if not: mechanical fault
96 Power balance, cylinder 6 Check other trouble codes, if not: mechanical fault
97 Power balance, cylinder 7 Check other trouble codes, if not: mechanical fault
98 Power balance, cylinder 8 Check other trouble codes, if not: mechanical fault
99 Accelerator pedal position (APP) sensor 2 supply voltage low Wiring, poor connections, APP sensor