Nige
Senior Member
The reason I was asking was because ground connections are notoriously difficult to troubleshoot. A multimeter can show continuity but the wire will not pass the required current for the circuit to operate.
My preference is to use a test lamp of something like 3-5A connected to battery positive to probe ground connections. If the lamp lights brightly then it is passing the rated current and you can be pretty certain that the ground connection is good.
This is only a thought but if the Engine and Transmission ECMs communicate via the CAN and Cat Datalinks I wonder if a power/ground issue on the Engine ECM side could affect the way the Transmission ECM registers “system voltage”.
I think that you would be wise to do the same checks of power & ground on the Engine ECM, even just to rule it out as being anything related to the problem.
My preference is to use a test lamp of something like 3-5A connected to battery positive to probe ground connections. If the lamp lights brightly then it is passing the rated current and you can be pretty certain that the ground connection is good.
This is only a thought but if the Engine and Transmission ECMs communicate via the CAN and Cat Datalinks I wonder if a power/ground issue on the Engine ECM side could affect the way the Transmission ECM registers “system voltage”.
I think that you would be wise to do the same checks of power & ground on the Engine ECM, even just to rule it out as being anything related to the problem.