BUS Communication With Engine Module

THEORY OF OPERATION:
The Transmission Control Module communicates with the Powertrain Control Module over the CCD bus. The controller continuously monitors the bus activity and receives the messages it needs. This code does not cause the transmission to go into limp in mode. However, it results in delayed 3 - 4 shift or early 4 - 3 shift for a few minutes after the engine is started, and no torque converter clutch operations for a few minutes after the engine is started.

LIMP-IN:
NO

WHEN MONITORED/SET CONDITIONS:
Every 7 milliseconds. Engine rpm must not be equal to zero. The code sets in approximately 10 seconds if no CCD messages are received for 10 seconds. The following conditions must be met for a successful OBDII trip:
- The engine must run for than 2 minutes.
- The turbine speed must be greater than 600 RPM or the output speed must be greater than 400 RPM.
- If the transmission is either cool or warm, all forward gears must be applied for 3.5 seconds each and the transmission must be in either park or neutral for 3.5 seconds.
- If the transmission is hot, all forward gears must be applied for 1.5 seconds each and the transmission must be in either park or neutral for 1.5 seconds.
- No MIL lamp trouble codes have occurred or reoccurred.

TRANSMISSION EFFECTS:
- Delayed upshifts and early downshifts.
- No torque convertor clutch operation.

POSSIBLE CAUSES:
- Open or short circuits between transmission control module and powertrain control module.
- CCD bus biasing problem (bus has to be properly biased by one of the vehicle's controllers).
- Powertrain control module CCD circuit problem.
- Transmission control module CCD circuit problem.