Transmission

Good morning.

The first thing I would do is clean the battery cables real well.

Low voltage will cause this issue and power comes from the battery.

Are there any codes stored?

Roy

https://www.2carpros.com/articles/everything-goes-dead-when-engine-is-cranked

You are welcome.

Will be here all day.

Roy

Okay, the 73 code is a serial data line code. In other words, there is no communication between modules. It looks like the issue is with the transmission control module. It could be just a connector needing to be cleaned or it may be the module itself.

The 700 code is a general code for a transmission fault. There is usually another code along with this code.

Roy

DTC U0073

DTC Descriptors

DTC U0073 00: High Speed Communication Bus.
DTC U0073 71: Control Module Communication Bus Off Invalid.
DTC U0073 72: Control Module Communication Bus Off Alive Counter Incorrect.

Circuit/System Description

The high speed GMLAN serial data circuits are high speed serial data buses used to communicate information between the control modules. Typical data transmission speeds must be high enough to ensure that a required real-time response is maintained. The high speed GMLAN serial data circuits also connect directly to the data link connector (DLC).

Conditions for Running the DTC

- Supply voltage to the modules are in the normal operating range.
- The vehicle power mode requires serial data communications.

Conditions for Setting the DTC

The module setting the DTC has attempted to establish communications on the GMLAN circuits more than 3 times.

Action Taken When the DTC Sets

- The module suspends all message transmission.
- The module uses default values for all parameters received on the serial data circuits.
- The module inhibits the setting of all other communication DTCs.

Conditions for Clearing the DTC

- 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.

Diagnostic Aids

- An intermittent condition is likely to be caused by a short on the high speed GMLAN serial data circuits.
- This DTC cannot be retrieved with a current status. Diagnosis is accomplished using the symptom Scan Tool Does Not Communicate with High Speed GMLAN Device.
- Refer to Data Link References for the specific modules using high speed GMLAN serial data.