• | Perform the Diagnostic System Check - Vehicle prior to using this diagnostic procedure. |
• | Review Strategy Based Diagnosis for an overview of the diagnostic approach. |
• | Diagnostic Procedure Instructions provides an overview of each diagnostic category. |
Circuit | Short to Ground | Open/High Resistance | Short to Voltage | Signal Performance |
---|---|---|---|---|
ECM B+ | 1* | 1* | -- | -- |
ECM Ground | -- | 1* | -- | -- |
PTLAN + | U0074* | U1818*, U189A | U0074* | -- |
PTLAN - | U0074* | U1818*, U189A | U0074* | -- |
* Other modules/DTCs will set with this fault. 1. Multiple DTCs including U1818 may set, and multiple symptoms including no start may occur |
Modules connected to the serial data circuits monitor for serial data communications during normal vehicle operation. Operating information and commands are exchanged among the modules. The modules have prerecorded information about what messages are needed to be exchanged on the serial data circuits, for each virtual network. The messages are supervised and also, some periodic messages are used by the receiver module as an availability indication of the transmitter module. Each message contains the identification number of the transmitter module.
DTC U1818 will set in the serial data gateway module (SDGM) when no communication is established with the ECM on the PTLAN serial data bus.
• | The system voltage is between 9-16 volts. |
• | The vehicle power mode master requires serial data communication to occur from this specific module. |
A supervised periodic message that includes the transmitter module availability has not been received.
The modules is never signaled, therefore the specific subsystems will not function.
• | A current DTC clears when the malfunction is no longer present. |
• | A history DTC clears when the module ignition cycle counter reaches the reset threshold of 50, without a repeat of the malfunction. |
• | When testing circuits to the SDGM access can be accomplished by removing the instrument panel center trim panel. Note that this procedure does not allow removal of the SDGM, only access to the connector. Refer to Instrument Panel Center Trim Panel Replacement . |
• | If the ECM is inoperative due to an open in the voltage or ground circuits then DTC U0100 will be set current in the power steering control module (PSCM). |
• | Different DTCs may set in different modules along with this DTC depending on where the fault occurs and the vehicle operating conditions when the fault occurs. |
Data Link Communications Description and Operation
Verify the following DTCs are not set in the modules as follows:
• | PSCM - U0100 |
• | SDGM - U189A |
⇒ | If any listed DTC is present, refer to Diagnostic Trouble Code (DTC) List - Vehicle to diagnose that DTC prior to this diagnostic. |
• | PTLAN + APM terminal 5 and EBCM terminal 33 |
• | PTLAN - APM terminal 1 and EBCM terminal 21 |
⇒ | If greater than the specified range, test the circuit for an open/high resistance. |
• | PTLAN + EBCM terminal 34 and SDGM terminal 13 |
• | PTLAN - EBCM terminal 22 and SDGM terminal 11 |
⇒ | If greater than the specified range, test the circuit for an open/high resistance. |
Perform the Diagnostic Repair Verification after completing the diagnostic procedure.
• | Control Module References for module replacement, setup, and programming |