Safety Warning
DIY auto repair can cause serious injury, fire, or vehicle damage. These guides are for informational purposes only. Always follow OEM torque specs, wear PPE, and consult a certified mechanic if you are unsure. You are solely responsible for your safety.
1995 GMC Forward Control 4.3 Z, AutomaticFACTORY OEM SERVICE PROCEDURE
Engine Performance DTCS (5.7L)
ENGINE PERFORMANCE DTCS (5.7L)
| OEM Code | Description |
|---|---|
| 13 | OPEN OXYGEN SENSOR CIRCUIT |
| 14 | COOLANT SENSOR SIGNAL VOLTAGE LOW |
| 15 | COOLANT SENSOR SIGNAL VOLTAGE HIGH |
| 16 | VSS BUFFER FAULT |
| 21 | TPS SIGNAL VOLTAGE HIGH |
| 22 | TPS SIGNAL VOLTAGE LOW |
| 24 | VSS - "C" & "K" SERIES EXCEPT 5.7L M/T |
| 24 | VSS - M/T |
| 24 | VSS TRANSMISSION OUTPUT SIGNAL - A/T |
| 28 | TRANSMISSION RANGE PRESSURE SWITCH |
| 31 | ENGINE SPEED GOVERNOR - "G" SERIES |
| 32 | EGR CIRCUIT ERROR BACKPRESSURE EGR WITH SOLENOID |
| 32 | EGR CIRCUIT ERROR WITH EVRV SOLENOID |
| 32 | EGR CKT ERROR - "C", "G", "K" SERIES W/ LINEAR EGR |
| 33 | MAP SENSOR SIGNAL VOLTAGE HIGH |
| 34 | MAP SENSOR SIGNAL VOLTAGE LOW |
| 35 | IDLE SPEED ERROR |
| 36 | IDLE SPEED ACTUATOR FAULT - A/T |
| 37 | TCC BRAKE SWITCH ON/OFF |
| 38 | TCC BRAKE SWITCH ON/OFF |
| 39 | TCC STUCK OFF - 4L80-E TRANSMISSION |
| 42 | IGNITION CONTROL |
| 43 | KNOCK SENSOR WITH SPARK CONTROL MODULE |
| 43 | KNOCK SENSOR WITHOUT SPARK MODULE (DUAL SENSORS) |
| 43 | KNOCK SENSOR WITHOUT SPARK MODULE (SINGLE SENSOR) |
| 44 | LEAN EXHAUST INDICATION |
| 45 | RICH EXHAUST INDICATION |
| 51 | PROM ERROR (FAULTY OR INCORRECT PROM) |
| 52 | FAULTY CALPAK |
| 52 | SYSTEM VOLTAGE HIGH |
| 53 | SYSTEM VOLTAGE HIGH |
| 54 | FUEL PUMP CIRCUIT |
| 55 | ECM/PCM ERROR |
| 58 | TRANSMISSION FLUID TEMPERATURE HIGH |
| 59 | TRANSMISSION FLUID TEMPERATURE LOW |
| 66 | 3-2 CONTROL SOLENOID CKT FAULT 4L60-E TRANSMISSION |
| 67 | TCC SOLENOID CIRCUIT CHECK - 4L60-E TRANSMISSION |
| 68 | OVERDRIVE RATIO ERROR - 4L80-E TRANSMISSION |
| 69 | TORQUE CONVERTER CLUTCH STUCK ON 4L60-E TRANSMISSION |
| 69 | TORQUE CONVERTER CLUTCH STUCK ON 4L80-E TRANSMISSION |
| 72 | VSS CIRCUIT LOSS TRANSMISSION OUTPUT SIGNAL |
| 73 | PRESSURE CONTROL SOLENOID (CURRENT ERROR) |
| 74 | TRANSMISSION INPUT SPEED ERROR 4L80-E TRANSMISSION |
| 75 | SYSTEM VOLTAGE LOW |
| 79 | TRANSMISSION FLUID TEMPERATURE HIGH |
| 81 | TRANSMISSION 2-3 ERROR |
| 82 | TRANSMISSION 1-2 ERROR |
| 83 | TCC SOLENOID CIRCUIT FAULT |
| 85 | UNDEFINED GEAR RATIO |
| 86 | LOW GEAR RATIO ERROR |
Factory Service Tools
Use the Manual With the Right Hardware
Pair factory procedures with proven DIY tools so the instructions are easier to execute.
Disclosure: Verified tool recommendations may earn an affiliate commission at no cost to you.
When to See a Mechanic
Stop DIY work and contact a certified mechanic immediately if any of the following apply:
- • You smell fuel, burning insulation, or see smoke.
- • Brakes feel soft, pull hard to one side, or make grinding noises.
- • The engine overheats, stalls repeatedly, or misfires under load.
- • You are missing required tools, torque specs, or safe lifting equipment.
- • You are not confident in the next step or safety outcome.
Rather have a pro handle this?
A certified mobile mechanic comes to your home or office. They bring the tools, you stay comfortable. No tow truck, no waiting room, no surprises.
Comes to youSame-day available12-month warranty
Get a Free QuoteNo obligation. See pricing before you book.