quote:

P0730-INCORRECT GEAR RATIO

Theory of Operation

The Transmission Control Module (TCM) constantly calculates the transmission ratio based on the input speed sensor
1 and 2 (N2-N3) signals and the calculated output shaft speed. The intent of this diagnostic is to detect if the
transmission is trying to mechanically shift INTO a lower gear then the TCM intends.
² When Monitored:
Engine RPM greater than 450 RPM, output speed greater than 180 RPM, no N2 - N3 input speed sensor
errors present, no gear selector lever errors present, no ABS system errors, and all wheel speeds above 450
RPM.
² Set Condition:
No shifting operation and detected gear is not the actual gear. No shifting operation - detected (calculated)
gear is less than actual (expected) gear, no plausible gear is calculated, actual turbine speed - calculated turbine
speed is greater than 300 RPM or calculated transmission ratio is above threshold. During an Upshift -
detected (calculated) gear is less than actual (expected) gear. During Downshift - detected (calculated) gear is
less than actual (expected) gear.

Possible Causes

INTERNAL TRANSMISSION PROBLEM
TRANSMISSION CONTROL MODULE
Always perform the Pre-Diagnostic Troubleshooting procedure before proceeding. (Refer to 21 - TRANSMISSION/
TRANSAXLE/AUTOMATIC - NAG1 - DIAGNOSIS AND TESTING)