Description
ECM has the memory function of the DTC memory, the air-fuel ratio feedback compensation value memory, the Idle Air Volume Learning value memory, etc. even when the ignition switch is turned OFF.

DTC DETECTION LOGIC
| DTC No. | Trouble diagnosis | DTC detecting condition | Possible cause |
|
P0603 |
ECM BACK UP/CIRCUIT (ECM power supply circuit) | ECM back-up RAM system does not function properly. |
|
DTC CONFIRMATION PROCEDURE
1.PRECONDITIONING
If DTC Confirmation Procedure has been previously conducted, always perform the following procedure before conducting the next test.
>> GO TO 2.
2.PERFORM DTC CONFIRMATION PROCEDURE
Is 1st trip DTC detected?
YES >> Go to EC, "Diagnosis Procedure".
NO >> INSPECTION END
1.INSPECTION START
Is the 1st trip DTC P0603 displayed again?
YES >> GO TO 2.
NO >> INSPECTION END
2.REPLACE ECM
>> INSPECTION END
Variable voltage control system (if so equipped)
CAUTION
Do not ground accessories directly to
the battery terminal. Doing so will bypass
the variable voltage control system
and the vehicle battery may not
charge completely.
Use electrical accessories with the engine
running to avoid discharging the
vehicle battery.
Your v ...
U0073 Communication bus a off
DTC Logic
DTC
Trouble diagnosis name
DTC detecting condition
Possible causes
U0073
Control Module Communication
Bus "A" Off
When the ignition switch is ON,
TCM detects a bus-off error
continuously for 2 seconds or
more.
Harness or connector
(CA ...