DTC 73

Fig. 159 Code 73: PCM-EBTCM/EBCM PWM Signal Fault.:

DTC 73: PCM-EBTCM/EBCM PMW Signal Fault:

CIRCUIT DESCRIPTION
Traction control is simultaneously controlled by the EBTCM on the vehicles equipped with the 4.6L Northstar, and the PCM. The PCM receives a "DESIRED TORQUE" request via a Pulse Width Modulated (PWM) signal from the EBTCM (CKT 594) requesting the desired torque level for proper traction control system operation. Torque reduction will be indicated if the duty cycle of the PWM signal is between 10% (100 % torque reduction) and 90% (no torque reduction and at least one (up to five) cylinder is requested to be disabled. The percent duty cycle will indicate the percent torque required. The PCM will selectively disable fuel to certain cylinders to achieve this reduction and communicate the actual torque output back to the EBTCM (CKT 595).

TEST CONDITION(S)
1. Tested continuously.

FAILURE CONDITION(S)
1. While Standing or Driving: PWM interface between EBTCM/EBCM and PCM is lost.

ACTION TAKEN
1. Code set.
2. "TRACTION DISABLED" message "ON."

A Code 73 may set if either CKT 594 or 595 is open, shorted to ground or shorted to voltage.

If CKT 595, Delivered Torque, is damaged and the EBTCM loses this input, a TCS Diagnostic Code 73 will be set. The PCM monitors the serial data line to see if the traction control has been disabled. If it has, the PCM will not set Code 93.

If CKT 594, Desired Torque is damaged and the PCM loses this input, the PCM monitors the serial data line to see if the traction control has been disabled. If not, the PCM sets a Code 93 and then tells the EBTCM/EBCM, via serial data, that there is a PWM circuit problem and the EBTCM/EBCM sets a Code 73.

TEST DESCRIPTION
Test numbers refer to circled numbers on the diagnostic chart.
1. Checks if the PCM Diagnostic Trouble Code 93 is set. If it is, there is likely a problem with CKT 594.
2. Checks for an open or high resistance in CKT 595.
3. Checks for a short to ground in CKT 595.
4. Checks for a short to voltage in CKT 595.
5. If no problem is found up until this point, CKT 594 should be checked.
6. Checks for an open or high resistance in CKT 594.
7. Checks for a short to ground in CKT 594.
8. Checks for a short to voltage in CKT 594.
9. If CKT 595 has not been checked, proceed to the left hand side of the trouble tree. If it has, continue downward. Problem is intermittent or in one of the controllers.
10. Checks if Code 73 and/or 93 are intermittent. If not, trouble is in either PCM or EBTCM.

DIAGNOSTIC AIDS
^ It is theoretically impossible for only a PCM Code 93 to set. If only a PCM Code 93 is present, either the TCS Code 73 has been cleared or there is a problem with the PCM.
^ A Code 73 may set by itself if the PCM PROM has been improperly installed.