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Transmission Information

If your mechanic tells you ........ you need a new transmission

You need to ask yourself: Did they scan your TCM for DTC’s ?

Did you know that on computer controlled vehicles a minor problem can feel like a major one. Especially with codes MLPS, TPS, or VSS. Even a PCM or PROM or a faulty charging system cam make your vehicle feel like it needs a new transmission and these are external fixes, internal fixes that are sometimes minor repairs that could be a TCCS, EPC, or OOS.

Sounds confusing doesn’t it ?

Here are a list of common transmission terms and abbreviations:

• DTC’s - Diagnostic Trouble Codes (Information that the computer gives you about a problem you have)
• EXTERNAL items:
• Fancy names for neutral safety switches
• MLPS - Manual lever position switch
• Without it the computer doesn’t know what gear you have selected
• PNP - Park / Neutral switch -same as MLPS
• TRS - Transmision range selector - same as MLPS
• Fancy names for accelerator lever
• TPS - Throttle position sendor
• This tells the computer how much gas you a applying. It also controls passing gear selection.
• TPP - Throttle position potentiometer - same as TPS
• FIPL - Fuel injection pump lever - same as TPS
• DBW - Drive by wire - same as TPS only fully electronic
• Fancy names for speedometer
• VSS - vehicle speed sensors
• This tells tells the computer how fast you are going so it knows when to shift
• TSS - Turbine speed sensor - same as VSS
• OSS - Output shaft speed - same as VSS
• ISS - Input speed sensor
• This tells the computer how fast the transmission is spinning.
• PSOM - Programmable speedometer odometer module
• This tells the computer speed with a tamper proof odometer readout.
• Fancy names for the computer
• PCM - Powertrain control module
• This computer can control motor and transmission
• TCM - Transmission control module
• This is the transmission computer
• VCM - Vehicle control module - same as PCM
• ECM - Engine control module
• This is usually engine control only
• TTVA - Transmission throttle valve actuator
• Tells the transmission how you are pressing on the throttle
• PROM - Programmable Read Only Memory
• This is the computer chip that goes into a PCM that contains the manufacturer’s engine and transmission settings for your specific vehicle’s options and features.
• INTERNAL items:
• EPC - Electronic pressure control
• This controls shift feel in all ranges
• TCCS - Torque converter clutch solenoid
• This controls clutch activation (“lockup”)
• TFT - Transmission fluid temperature
• This usually means transmission has overheated
• TOT - Transmission oil temperature - same as TFT
• PCS - Pressure control solenoid - same as EPC
• SS1-5 / SSA-E - Shift solenoid
• This tells you that there is a fault on a specific solenoid

All of the above items control shift strategy

• OTHER:
• EGR - Exhaust gas re-circulation
• Emission fault
• SRS - Supplemental restraint system
• Air bag
• RABS - Rear wheel antilock brake system
• Brake fault
• SES - Service engine soon
• Maintenance required indicator

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