Powertrain Controls - ECM/PCM

DTC 72 Loss Of Serial Data:

Loss Of Serial Data:

CIRCUIT DESCRIPTION
Serial data is the method of communication by components or modules to each other or to a Tech 1 scan tool. The serial data communication bus consists of four components or modules: the Powertrain Control Module (PCM), Diagnostic Energy Reserve Module (DERM), Electronic Brake Control Module (EBCM), and the Instrument Panel Cluster (IPC). The IPC is the master of this network and sends out a message through serial data (CKT 800) to the other modules. Each module in return responds back to the IPC with updated information used by the IPC. If any of the modules do not respond to the IPC, a DTC is set in each applicable module.

DIAGNOSTIC TROUBLE CODE (DTC) 72 WILL SET WHEN
^ The IPC does not receive 25 valid responses from the PCM.
^ System voltage is greater than 6.8 volts.
^ Above conditions are met for 5 seconds.

DIAGNOSTIC TROUBLE CODE (DTC) 72 WILL SET WHEN
The IPC receives 25 valid responses from the PCM.

DTC CHART TEST DESCRIPTION
Number(s) below refer to circled number(s) on the diagnostic chart.

1. When serial data is lost, the IPC telltales will all be illuminated. This is a good indication when serial data is lost to the IPC.
2. If the Tech 1 scan tool cannot read serial data, be sure the scan tool is working properly on another vehicle.
3. If PCM serial data is available, then the circuit may be open to the IPC. If OK, then the fault is in the I/P cluster or circuitry.
4. If the scan tool is functioning properly and CKT 800 is OK, the EPROM or PCM may be at fault causing loss of serial data.

DIAGNOSTIC AIDS
^ Move PCM connectors while watching Tech 1 scan tool to see if serial data is lost. When serial data is lost, the IPC telltales will all be illuminated. This is a good indication when serial data is lost to the I/P cluster.
^ An "Intermittent" problem may be caused by a poor connection, rubbed through wire insulation, or a wire that is broken inside the insulation.
^ Any circuitry, that is suspected as causing the intermittent complaint, should be thoroughly checked for improper mating, broken locks, improperly formed or damaged terminals, or physical damage to the wiring harness.