Is your "Check Engine Light" on? An illuminated "Malfunction Indicator Lamp" (or MIL ) means a fault has been detected in the engine control system and one or more "diagnostic trouble codes" (DTCs) are stored in the engine's computer. Depending on the nature of the fault, the lamp may come on and go off, remain on continuously or flash. Some types of intermittent faults will make the lamp come on only while the fault is occurring. When the fault goes away, the lamp goes off. Other types of problems will turn the light on, and it will remain on until the fault is diagnosed and repaired.
The Check Engine light has proven to be a great annoyance to many motorists (as well as professional technicians) because it seems to have a mind of its own. For one thing, it doesn't tell you anything about the nature of the problem or what the trouble code might be. It could be something serious - or it might not. There is no way to know without performing a diagnostic test on the system. Consequently, you don't know if you should stop immediately or ignore the light and keep driving. If no other warning lights are on, and the engine seems to be running normally (no unusual noises, smells, vibrations, etc.), it is probably safe to assume the problem is minor and won't hinder your ability to continue driving. But sooner or later, you should have the cause of the light investigated.
Whenever the Check Engine light comes on, a "diagnostic trouble code" (DTC) or fault code is recorded in the powertrain control module (PCM) memory. The trouble code has a number that corresponds to the type of fault. Some problems can generate more than one trouble code, and some vehicles may suffer from multiple problems that also set multiple trouble codes.
SETTING TROUBLE CODES
In most older vehicles (those made before 1996), disconnecting the computer power source or disconnecting a battery cable could erase fault codes -- at least temporarily until the trouble code resets and turns the check engine light back on. But on many newer vehicles, you do NOT want to disconnect the battery because doing so can wipe out the computer's memory settings as well as the trouble codes. This may affect the operation of the transmission, climate control system and other functions.
In most newer computer systems, fault codes are stored in a "nonvolatile" memory that is not lost if the battery is disconnected. The trouble codes remain intact until they are cleared using a scan tool
Diagnostic Trouble Code numbers are read by plugging a code reader or scan tool into the vehicle diagnostic connector (usually located under the instrument panel near the steering column). The presence of a code will turn on the Check Engine Light. The light will remain on until the code has been erased. The code number does not tell you which part has failed. It only indicates a possible fault has been detected in the circuit, system or sensor described. Further testing is usually required to isolate the fault BEFORE repairs are made. For diagnostic charts and vehicle specific repair information, refer to a service manual, or the OEM technical website
DTC CODES P0800 to P0899 (Transmission Codes)
P0801....Reverse Inhibit Control Circuit
P0803....1-4 Upshift (Skip Shift) Solenoid Control Circuit
P0804....1-4 Upshift (Skip Shift) Lamp Control Circuit
P0805....Clutch Position Sensor Circuit (Click Here for help diagnosing clutch problems)
P0806....Clutch Position Sensor Circuit Range/Performance
P0807....Clutch Position Sensor Circuit Low
P0808....Clutch Position Sensor Circuit High
P0809....Clutch Position Sensor Circuit Intermittent
P0810....Clutch Position Control Error
P0811....Excessive Clutch Slippage
P0812....Reverse Input Circuit
P0813....Reverse Output Circuit
P0814....Transmission Range Display Circuit
P0815....Upshift Switch Circuit
P0816....Downshift Switch Circuit
P0817....Starter Disable Circuit
P0818....Driveline Disconnect Switch Input Circuit
P0820....Gear Lever X-Y Position Sensor Circuit
P0821....Gear Lever X Position Circuit
P0822....Gear Lever Y Position Circuit
P0823....Gear Lever X Position Circuit Intermittent
P0824....Gear Lever Y Position Circuit Intermittent
P0825....Gear Lever Push-Pull Switch (Shift Anticipate)
P0830....Clutch Pedal Switch 'A' Circuit
P0831....Clutch Pedal Switch 'A' Circuit Low
P0832....Clutch Pedal Switch 'A' Circuit High
P0833....Clutch Pedal Switch 'B' Circuit
P0834....Clutch Pedal Switch 'B' Circuit Low
P0835....Clutch Pedal Switch 'B' Circuit High
P0836....Four Wheel Drive (4WD) Switch Circuit
P0837....Four Wheel Drive (4WD) Switch Circuit Range/Performance
P0838....Four Wheel Drive (4WD) Switch Circuit Low
P0839....Four Wheel Drive (4WD) Switch Circuit High
P0840....Transmission Fluid Pressure Sensor/Switch 'A' Circuit
P0841....Transmission Fluid Pressure Sensor/Switch 'A' Circuit Range/Performance
P0842....Transmission Fluid Pressure Sensor/Switch 'A' Circuit Low
P0843....Transmission Fluid Pressure Sensor/Switch 'A' Circuit High
P0844....Transmission Fluid Pressure Sensor/Switch 'A' Circuit Intermittent
P0845....Transmission Fluid Pressure Sensor/Switch 'B' Circuit
P0846....Transmission Fluid Pressure Sensor/Switch 'B' Circuit Range/Performance
P0847....Transmission Fluid Pressure Sensor/Switch 'B' Circuit Low
P0848....Transmission Fluid Pressure Sensor/Switch 'B' Circuit High
P0849....Transmission Fluid Pressure Sensor/Switch 'B' Circuit Intermittent
P0850....Park/Neutral Switch Input Circuit
P0851....Park/Neutral Switch Input Circuit Low
P0852....Park/Neutral Switch Input Circuit High
P0853....Drive Switch Input Circuit
P0854....Drive Switch Input C ircuit Low
P0855....Drive Switch Input Circuit High
P0856....Traction Control Input Signal (Click Here for help diagnosing traction control faults)
P0857....Traction Control Input Signal Range/Performance
P0858....Traction Control Input Signal Low
P0859....Traction Control Input Signal High
P0860....Gear Shift Module Communication Circuit
P0861....Gear Shift Module Communication Circuit Low
P0862....Gear Shift Module Communication Circuit High
P0863....TCM Communication Circuit
P0864....TCM Communication Circuit Range/Performance
P0865....TCM Communication Circuit Low
P0866....TCM Communication Circuit High
P0867....Transmission Fluid Pressure (Click Here for help diagnosing automatic transmission faults)
P0868....Transmission Fluid Pressure Low
P0869....Transmission Fluid Pressure High
P0870....Transmission Fluid Pressure Sensor/Switch "C" circuit
P0871....Transmission Fluid Pressure Sensor/Switch "C" Circuit Range/Performance
P0872....Transmission Fluid Pressure Sensor/Switch "C" circuit Low
P0873....Transmission Fluid Pressure Sensor/Switch "C" circuit High
P0874....Transmission Fluid Pressure Sensor/Switch "C" circuit Intermittent
P0875....Transmission Fluid Pressure Sensor/Switch "D" circuit
P0876....Transmission Fluid Pressure Sensor/Switch "D" Circuit Range/Performance
P0877....Transmission Fluid Pressure Sensor/Switch "D" circuit Low
P0878....Transmission Fluid Pressure Sensor/Switch "D" circuit High
P0879....Transmission Fluid Pressure Sensor/Switch "D" circuit Intermittent
P0880....TCM Power Input Signal
P0881....TCM Power Input Signal Range/Performance
P0882....TCM Power Input Signal Low
P0883....TCM Power Input Signal High
P0884....TCM Power Input Signal Intermittent
P0885....TCM Power Relay Control Circuit/Open
P0886....TCM Power Relay Control Circuit Low
P0887....TCM Power Relay Control Circuit High
P0888....TCM Power Relay Sense Circuit
P0889....TCM Power Relay Sense Circuit Range/Performance
P0890....TCM Power Relay Sense Circuit Low
P0891....TCM Power Relay Sense Circuit High
P0892....TCM Power Relay Sense C ircuit Intermittent
P0893....Multiple Gears Engaged
P0894....Transmission Component Slipping
P0895....Shift Time Too Short
P0896....Shift Time Too Long
P0897....Transmission Fluid Deteriorated (Click Here for information about automatic transmission fluid)
P0898....Transmission Control System MIL Request Circuit Low
P0899....Transmission Control System MIL Request Circuit High
Remember that these Automotive DTC trouble codes are just a starting point, further diagnostics will be required to find the root cause of the check engine light and the setting of the trouble code. Please visit our forums for more detailed information on DTC trouble codes.
