TO: All ATP Technicians
FROM: James Strong, Technical Support Manager
RE: New Automatic Transmission Pressure Switch Manifolds
These pressures switch manifolds (PSM) are attached to the valve body and is used to signal the manual valve position to the PCM (Powertrain Control Module). Depending on the position of the manual valve, fluid is routed to the PSM. It is this fluid that opens and closes the fluid pressure switches within the PSM. Depending on the vehicle and transmission, the PCM uses information from the on/off positioning of the switches to adjust line pressure, TCC (torque converter clutch) apply and to control shift solenoid operation.
The purpose of the PSM is to provide a binary signal to the PCM indicating the gear range selected by the vehicle operator. An open circuit is represented by a binary code "1" and measures 12 volts while a grounded circuit binary code is "0" and measures out to 0 volts. When the position of the selector lever changes, the manual valve also changes and routes fluid to different switches in the switch assembly.
A Transaxle Fluid Pressure Switch Manifold malfunction will set a DTC (diagnostic trouble code) P1810 and the PCM will command the following default actions:
- DTC P1810 will be stored in the PCM history.
- Freeze shift adapts.
- Assume D4 (drive 4) shift pattern.
- Inhibit TCC engagement.
- Elevate line pressure.
In addition, corrosion and/or oxidation around the electrical connection harness of the PSM can also lead to PSM malfunction.
Depending if the vehicle is front wheel drive or rear wheel drive, the PSM (Pressure Switch Manifold) is located by the valve body. For front wheel drive vehicles, the PSM is located inside the side-cover. For these types of vehicles, the transaxle must be lowered or removed to service the PSM.
On rear wheel drive vehicles, the transmission pan must be removed and the PSM can be serviced at the valve body. These types of vehicles do not require the lowering or removal of the transmission. (See Figures)
ATP-Inc has introduced (5) new part numbers for these failure prone automatic transmission pressure switch manifolds listed below:
Part No. JE-9 1993-08 GM 4L60/65/70-E Transmissions
Part No. JE-10 1991-08 GM 4L80/85-E Transmissions
Part No. JE-11 1997-02 GM 4T65-E Transaxles
Part No. JE-12 1995-Up GM 4T40-E Transaxles
Part No. JE-13 1993-99 GM 4T80-E Transaxles
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