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.
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HOMESERVICE MANUALSCHEVROLET1995FORWARD CONTROL 7.4 NREPAIR AND DIAGNOSISEXTERNAL PAGESDIFFERENT CARSECTION 115 (ENGINE CONTROLS - TESTS W/CODES - 6.5L DIESEL)
1995 Chevrolet Forward Control 7.4 N
Section 115 (Engine Controls - Tests W/Codes - 6.5L Diesel)
1995 Chevrolet Forward Control 7.4 NSECTION Section 115 (Engine Controls - Tests W/Codes - 6.5L Diesel)
WARNING: This page does not describe the selected car, but rather 10 other vehicles, including the 1995 GMC Yukon, 1995 GMC Suburban, 1995 GMC Pickup, 1995 GMC Cab & Chassis, and 1995 GMC C3500 HD. However, it is still accessible from the selected car via links, so may be relevant.
- Introduction
- Self-Diagnostic System
- Diagnostic Trouble Code Charts
- Notes
- On-Board Diagnostic (OBD) System Check (Models With Pcm)
- Chart A-1, No Mil (Service Engine Soon Light) (Models W/ Pcm)
- Chart A-2, No Scan Data, Mil (Service Engine Soon) On At All Times Or Will Not Flash Mil (Models With Pcm)
- Chart A-3, Engine Cranks But Will Not Run
- EGR Control Pressure/BARO Sensor Output Check
- DTC 13, Engine Shutoff Solenoid Circuit Fault
- DTC 14, ECT Sensor Circuit Low (High Temperature Indicated)
- DTC 15, ECT Sensor Circuit High (Low Temperature Indicated)
- DTC 16, Vehicle Speed Signal Buffer Fault
- DTC 17, High Resolution Circuit Fault
- DTC 18, Pump Cam Reference Pulse Error
- DTC 19, Crankshaft Position Reference Error
- DTC 21, App No. 1 Circuit High (Models With Pcm)
- DTC 22, App No. 1 Circuit Low (Models With Pcm)
- DTC 23, App No. 1 Circuit Range Fault
- DTC 24, VSS Circuit Low (Transmission Output Speed Signal)
- DTC 25, Accelerator Pedal Position (App) No. 2 Circuit High
- DTC 26, Accelerator Pedal Position (App) No. 2 Circuit Low
- DTC 27, App No. 2 Circuit Range Fault
- DTC 28, Transmission Range Pressure Switch Circuit Fault
- Transmission Range Pressure Switch Combinations
- DTC 29, Glow Plug Relay Circuit Fault
- DTC 31, EGR Control Pressure/BARO Sensor CKT Low (High Vac)
- DTC 32, EGR Circuit Error
- DTC 33, EGR Control Pressure/BARO Sensor CKT High (Low Vac)
- DTC 34, Injection Timing Stepper (Its) Motor Circuit Fault
- DTC 35, Injection Pulse Width Error (Response Time Short)
- DTC 36, Injection Pulse Width Error (Response Time Long)
- DTCS 37/38, TCC Brake Switch Stuck On/Off
- DTC 39, TCC Stuck Off (4L80-E)
- DTC 41, Brake Switch Circuit Fault
- DTC 42, Fuel Temp Circuit Low (High Temp Indicated)
- DTC 43, Fuel Temp Circuit High (Low Temp Indicated)
- DTC 44, EGR Pulse Width Error
- DTC 45, EGR Vent Error
- DTC 46, Malfunction Indicator Light (Mil) Circuit Fault
- DTC 47, IAT Sensor Circuit Low (High Temperature Indicated)
- DTC 48, IAT Sensor Circuit High (Low Temperature Indicated)
- DTC 49, Service Throttle Soon Light Circuit Fault
- DTC 51, Prom Problem (Faulty Or Incorrect Prom)
- DTCS 52/53, System Voltage High Long
- DTC 54, Pcm Fuel Circuit Error
- DTC 56, Injection Pump Calibration Resistor Error
- DTC 57, Pcm 5-Volt Shorted
- DTC 58, Transmission Fluid Temp Sensor Circuit Low (High Temp Indicated) - 4L60-E & 4L80-E
- DTC 59, Transmission Fluid Temp Sensor Circuit High (Low Temp Indicated) - 4L60-E & 4L80-E
- DTC 61, Turbo Boost Sensor Circuit High
- DTC 62, Turbo Boost Sensor Circuit Low
- DTC 63, App No. 3 Circuit High (Models With Pcm)
- DTC 64, App No. 3 Circuit Low (Models With Pcm)
- DTC 65, App No. 3 Circuit Range Fault
- DTC 66, 3-2 Control Solenoid Circuit Fault (4L60-E)
- DTC 67, TCC Solenoid Circuit Fault (4L60-E)
- DTC 68, Transmission Component Slipping (4L80-E)
- DTC 69, TCC Stuck On (4L60-E)
- DTC 69, TCC Stuck On (4L80-E)
- DTC 71, Set/Coast Switch Fault (Models With Pcm)
- DTC 72, Speed Sensor Circuit Loss (Trans Output Speed Signal) - 4L60-E & 4L80-E
- DTC 73, Pressure Control Solenoid Circuit (Current Error)
- DTC 74, Transmission Input Speed Sensor Circuit (4L80-E)
- DTC 75, System Voltage Low
- DTC 76, Resume/ACCEL Switch Fault
- DTC 78, WASTEGATE Solenoid Fault
- DTC 79, Transmission Fluid OVERTEMP - 4L60-E & 4L80-E
- DTC 81, 2-3 Shift Solenoid Circuit Fault - 4L60-E & 4L80-E
- DTC 82, 1-2 Shift Solenoid Circuit Fault - 4L60-E & 4L80-E
- DTC 83, TCC PWM Solenoid Circuit Fault - 4L60-E & 4L80-E
- DTC 84, Accelerator Pedal Position (App) Circuit Fault
- DTC 85, Undefined Ratio Error (4L80-E)
- DTC 86, Low Ratio Error (4L80-E)
- DTC 87, High Ratio Error (4L80-E)
- DTC 88, TDC Offset Error
- DTC'S 91-98, Cylinder Balance Fault
- DTC 99, App No. 2 (5-Volt Reference Fault)
- Wiring Diagrams
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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.