P0730

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.
- 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.
- 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.

Diagnostic Test
1. CHECK FOR INTERNAL TRANSMISSION PROBLEM
Determine if there are any Transmission mechanical problems present.
Remove the Transmission Oil Pan and inspect for excessive debris or a plugged Transmission Oil Filter.
Is there any Transmission mechanical problems present?
Yes >>Repair as necessary. Perform NAG1 TRANSMISSION VERIFICATION TEST. Transmission Verification Test
No >>Using the schematics as a guide, check the Transmission Control Module (TCM) pins, terminals, and connectors for corrosion, damage, or terminal push out. Pay particular attention to all power and ground circuits. If no problems are found, replace the TCM. Perform NAG1 TRANSMISSION VERIFICATION TEST. Transmission Verification Test