Got a quick question for you guys, why does my check engine light come on when I'm just going down the road at a constant mph but then when I give it gas it goes off?

 

here what you can do gives code so we tell you what going on

OBD-I is pre 96 vintage truck coding use OBD-II for trucks of 96 & later years & requires a scan tool to read them.


The Data Link connector is located below the steering wheel lower left rim of the dash just about knee cap height.


Use a jumper (paperclip, etc) to connect these terminals. The connection/removal of the jumper between terminals (A&B) should be done with the ignition switch OFF. Also to prevent potential volt spike to PCM remove clip with Key OFF also.Once jumper is installed then turn key to on/run (not full start) to begin the flashing sequence


The Service Engine Soon light will flash Code 12 three times to indicate that the diagnostics are working. Trouble codes will then follow, one at a time, three times each. DTC 12 will only appear if there are no other codes.


2 The codes appear in numerical order, and each code repeats itself three times before the next begins. This is different from some other ECM's.


3. It is helpful to the diagnostic process to know when codes are setting, particularly if there is more than one. Hence, clearing the codes is something you may wish to do. Clearing the codes may be accomplished by simultaneously depressing the brake and accelerator pedals fully while the PCM is in diagnostic mode (terminals A and B connected). It will not appear that you have cleared the codes until the next time you power up in diagnostic mode, however.








DTC 13 - Engine Shutoff Solenoid Circuit Fault
DTC 14 - Engine Coolant Temperature (ECT) Sensor Circuit Low (High Temp)
DTC 15 - Engine Coolant Temperature (ECT) Sensor Circuit High (Low Temp)
DTC 16 - Vehicle Speed Sensor Buffer Fault
DTC 17 - High Resolution Circuit Fault
DTC 18 - Pump Cam Reference Pulse Error
DTC 19 - Crankshaft Position Reference Error
DTC 21 - Accelerator Pedal Position 1 Circuit High
DTC 22 - Accelerator Pedal Position 1 Circuit Low
DTC 23 - Accelerator Pedal Position 1 Circuit Range Fault
DTC 24 - Vehicle Speed Sensor Circuit Low (Output Speed Signal)
DTC 25 - Accelerator Pedal Position 2 Circuit High
DTC 26 - Accelerator Pedal Position 2 Circuit Low
DTC 27 - Accelerator Pedal Position 2 Circuit Range Fault
DTC 28 - Transmission Range Pressure Switch Circuit
DTC 29 - Glow Plug Relay Fault
DTC 31 - EGR Control Pressure/Baro Sensor Circuit Low (High Vacuum)
DTC 32 - EGR Circuit Error
DTC 33 - EGR Control Pressure/Baro Sensor Circuit High
DTC 34 - Injection Timing Stepper Motor Fault
DTC 35 - Injection Pulse Width Error (Time Short)
DTC 36 - Injection Pulse Width Error (Time Long)
DTC 37 - TCC Brake Switch Stuck "ON"
DTC 38 - TCC Brake Switch Stuck "OFF"
DTC 39 - TCC Stuck "OFF"
DTC 41 - Brake Switch Circuit Fault
DTC 42 - Fuel Temperature Circuit Low (High Temp)
DTC 43 - Fuel Temperature Circuit High (Low Temp)
DTC 44 - EGR Pulse Width Error
DTC 45 - EGR Vent Error
DTC 46 - Malfunction Indicator Lamp (MIL) Circuit Fault
DTC 47 - Intake Air Temperature Sensor Circuit Low (High Temp )
DTC 48 - Intake Air Temperature Sensor Circuit High (Low Temp )
DTC 49 - Service Throttle Soon Lamp Circuit Fault
DTC 51 - PROM Error
DTC 52 - System Voltage High Long
DTC 53 - System Voltage High
DTC 54 - PCM fuel circuit error
DTC 56 - Injection Pump Calibration Resistor Error
DTC 57 - PCM 5 Volt Shorted
DTC 58 - Transmission Fluid Temp Circuit Low
DTC 59 - Transmission Fluid Temp Circuit High
DTC 61 - Turbo Boost Sensor Circuit High
DTC 62 - Turbo Boost Sensor Circuit Low
DTC 63 - Accelerator Pedal Position 3 Circuit High
DTC 64 - Accelerator Pedal Position 3 Circuit Low
DTC 65 - Accelerator Pedal Position 3 Circuit Range Fault
DTC 68 - Transmission Component Slipping
DTC 69 - TCC Stuck "ON"
DTC 71 - Set/Coast Switch Fault (Cruise Control)
DTC 72 - Vehicle Speed Sensor Circuit Loss (Output Speed Signal)
DTC 73 - Pressure Control Solenoid Circuit (Current Error)
DTC 74 - Transmission Input Speed (TIS) Sensor Circuit


DTC 75 - System Voltage Low
DTC 76 - Resume/Accel Switch Fault (Cruise Control)
DTC 78 -Turbo Wastegate Solenoid Fault