CD4E FAQ
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CD4E OBD-II Information -
TRANSMISSION INPUTS
The Analog Transmission Range (TR) sensor provides a single analog input to the PCM. The voltage corresponds
to the driver-selected gear position (Park, Rev, Neutral, OD, 2, 1). This input is checked for opens and shorts.
(P0707, P0708)
The Turbine Shaft Speed (TSS) sensor and Output Shaft Speed (OSS) sensors are analog inputs that are
checked for rationality. If the engine rpm is above the torque converter stall speed and engine load is high, it can be
inferred that the vehicle must be moving. If there is insufficient output from the TSS sensor, a malfunction is
indicated (P0715). If there is insufficient output from the OSS sensor, a malfunction is indicated (P0720).
TRANSMISSION OUTPUTS
Shift Solenoids
The Shift Solenoid (SSA and SSB) output circuits are checked for opens and shorts by the PCM by monitoring the
status of a feedback circuit from the output driver (P0750 SSA, P0755 SSB).
All vehicle applications will utilize an inductive signature circuit to monitor the shift solenoids functionally. The ISIG
circuit monitors the current signature of the shift solenoid as the solenoid is commanded on. A solenoid that
functions properly will show a characteristic decrease in current as the solenoid starts to move. If the solenoid is
malfunctioning, the current will not change (P1714 SSA, P1715 SSB). The ISIG test runs in conjunction with the
other transmission functional tests. The lack of communication between the ISIG chip and the PCM
microprocessor is also monitored (P1636).
Torque Converter Clutch
The Torque Converter Clutch (TCC) output circuit is a duty-cycled output that is checked electrically for opens and
shorts by the PCM by monitoring the status of a feedback circuit from the output driver (P0743).
The PWM used to control CD4E's TCC does not have sufficient inductive signature, therefore on these
applications the TCC solenoid is functionally tested by monitoring converter slip. If the TCC is failed on when
commanded off, a P1742 fault code will be stored. If the TCC is failed off when commanded on, a P0741 fault code
will be stored.
Electronic Pressure Control
The EPC solenoid is a variable force solenoid that controls line pressure in the transmission. The EPC solenoid
has a feedback circuit in the PCM that monitors EPC current. If the current indicates a short to ground (low
pressure), engine torque may be reduced to prevent damage to the transmission. (P0962, PCA)
TFT - Transmission Fluid Temperature sensor. Used byt the PCM to determines shift point characteristics based on the oil temperature of the transaxle.
From the `98 Ford Service CD -
"The MIL is illuminated for all emissions related electrical component malfunctions. For malfunctions attributable to a mechanical component (such as a clutch, gear, band, valve, etc.), some transmissions are capable of not commanding the mechanically failed component and providing the remaining maximum functionality (functionality is reassessed on each power up)- in such case a non-MIL Diagnostic Trouble Code (DTC) will be stored and, if so equipped, a Transmission Control Indicator Light (TCIL) will flash."
What this basically means, is that the CEL will illuminate, and stay that way, during an emmissions related electrical component faliure or malfunction. That is until the PCM memory is either cleared manually or the fault is not detected after two consecutive drive cycles.
If there is a mechanical failure, in the tranny, it will cause the TCIL (O/D light) to flash, which means that the PCM has stored a code indicating which fault it was. But!! This code will be cleared once the engine is turned off.
So. If your O/D light flashed, there was a code there to be read. If you turned your engine off before you could actually read that code, that code would disappear. If when you started your car again and the CEL was not on or the O/D light did not flash, there is nothing there to read. You will have to wait until the fault happens again.
Last edited by unisys12; 07/27/04 01:27 AM.
