1, 2 and 3 Digit Codes: 75

Name of Code:
75 - Overheat Shift Schedule In Use (97 MY only)

When Monitored:
Whenever the engine is running.

Set Condition:
Immediately once 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.

This code is an information fault code only and is being set to aid the technician in determining root cause of a customer driveability issue.
This 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 area.

Transmission Effects:
Information fault code for 97MY only - Overheat shift schedule was activated, no limp-in condition occurs. 2nd gear partial EMCC above 25 MPH, 3rd gear EMCC from 28-43 MPH, delayed 3-4 upshift at 43 MPH, early 4-3 coastdown at 41 MPH, EMCC operation under all conditions above 25 MPH except at closed throttle or 1st gear.

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