Allison Transmission Motorhome Series Operator's Manual page 82

Code Listings And Procedures
(Allison 4
P2637, P2641
Torque
Management
Feedback
Signal Fault
P2740
Retarder Oil
Temperature
Hot
P2742, P2743
Retarder Oil
Temperature
Sensor Circuit
Fault
P278A
Kickdown
Switch Circuit
P2793
Gear Shift
Direction
Circuit
th
Generation Controls) (cont'd)
1. Check that no unauthorized engine power upgrades
were made.
2. Check that engine software is compatible with
transmission torque requirements, otherwise:
a. Recalibrate engine controller with compatible
software, or
b. Reduce engine power and torque ratings.
1. Check:
a. Transmission fluid level is correct.
b. Retarder apply system is not allowing retarder and
throttle to be applied at the same time.
c. Vehicle manufacturer's transmission oil cooler is
adequately sized for heat load.
1. Check:
a. Retarder temperature measured with Allison DOC™
diagnostic tool is consistent with code, or determine
if code is active using the shift selector.
b. Retarder temperature sensor connector is tight,
clean, and undamaged.
c. TCM connector is tight, clean, and undamaged.
d. Temperature sensor circuit has no opens,
shorts-between-wires, or shorts-to-ground.
1. Check input wiring, switches, and connectors to
determine why kickdown input is not being sent to the
TCM.
1. Check:
a. Shift selector connector is tight, clean, and
undamaged.
b. TCM connector is tight, clean, and undamaged.
c. Gear shift direction circuit has no opens,
shorts-between-wires, or shorts-to-ground.
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