The Class II serial data link is configured in a ring used to communicate information between control modules. The controllers on the Class II link use a variable pulse width modulated square wave of 0-7 volts for communication. Zero volts equals a low state or logic 0, and 7 volts equals a high state or logic 1. The electronic brake and traction control module (EBTCM), powertrain control module (PCM) and sensing and diagnostic module (SDM) monitor the Class II link for low and high voltage faults.
DTC Parameters
DTC U1301 will set if the EBTCM, PCM or SDM detected the Class II circuit in the high state for too long (Class II circuit shorted to voltage) when:
| • | Condition exists for greater than 4 seconds for EBTCM, 2 seconds for PCM and SDM. |
| • | Ignition is On. |
DTC U1301 diagnostic runs continuously with ignition On.
DTC U1301 is a type C DTC.
Diagnostic Aids
If the scan tool can communicate with the EBTCM, PCM, or SDM, then the Class II link is not currently shorted to voltage.
Inspect the wiring harness for signs of chafing or broken insulation.
Important: The controller name won't be displayed until the scan tool initially received the correct controller ID over the link upon ignition On.
Important: The BCM CANNOT set U1301.
To locate an intermittent problem, use the scan tool to monitor any of the controllers on the Class II link located under DIAGNOSTIC CIRCUIT CHECK - - - CLASS II MESSAGE MONITOR with ignition On, engine Off. INACTIVE will be displayed on all controllers if the link is shorted to voltage.
