P1738 (75) - High Temperature Operation Activated

Name of Code:
P1738 (75) - High Temperature Operation Activated

When Monitored:
Whenever the engine is running.

Set Condition:
Immediately when the Overheat shift schedule is activated.

Theory of Operation:
If the transmission oil temperature rises above 240 °F, the overheat shift schedule is activated (See Transmission Operation as a function of Transmission Oil Temperature) and the fault code is set. The code is an information fault code only and is being set to aid the technician in determining root cause of a customer driveability issue. The code is also intended to alert the technician to determine if a cooling system malfunction has occurred or if an additional transmission air to oil cooler should be added to the vehicle if the customer regularly drives in a manner that overheats the transmission. Extended operation above 240 °F will reduce the durability of the transmission and should be avoided. Correcting the cooling system malfunction or installing an additional transmission oil cooler will improve transmission durability especially for customers who operate in city/construction stop and go traffic, tow trailers regularly, drive aggressively in low gear or drive regularly in mountainous areas.

Transmission Effects:
Information only code. Overheat shift schedule was activated, no limp-in condition occurs. See description of overheat shift schedule.

Possible Causes:
- Transmission Overfilled with Oil
- Engine cooling fan failure
- Engine thermostat stuck closed
- Radiator corroded or packed with dirt
- Transmission cooler corroded or packed with dirt
- Transmission Oil Cooler Plugged
- Driving pattern requires additional transmission cooling (See Theory of Operation for typical driving patterns that can cause overheating)