4L80E Codes Cheat Sheet: Codes and Fixes

This is your 4L80E code reference. Each code with what it means, what fails, and how to fix it. Bookmark this.

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How to use this guide

When you have a code:

Before buying parts:

P0700: TCM Request MIL

What it means:

  • Generic "TCM has a problem"
  • Pull additional codes

Fix:

  • Read additional TCM codes
  • Address specific code first

P0717: Input Speed Sensor Circuit No Signal

What it means:

  • ISS not communicating
  • TCM can't see input speed

Diagnosis:

Fix:

  • Replace ISS: $50-150
  • Or repair wiring: minimal cost

P0722: Output Speed Sensor Circuit No Signal

What it means:

  • OSS not communicating
  • Vehicle speed unknown

Diagnosis:

  • Same procedure as ISS
  • Different sensor location

Fix:

  • Replace OSS: $50-150
  • Or repair wiring

P0723: Output Speed Sensor Intermittent

What it means:

  • OSS dropping signal randomly

Fix:

  • Often connector issue
  • Sometimes failing sensor
  • Replace sensor or repair connector

P0731: Gear 1 Incorrect Ratio

What it means:

  • 1st gear slipping or sensor mismatch
  • Often clutch issue

Diagnosis:

Fix:

P0732: Gear 2 Incorrect Ratio

What it means:

  • 2nd gear slip
  • Often intermediate band wear

Diagnosis:

Fix:

  • HD intermediate band
  • Sometimes full rebuild
  • $200-2,500

P0733: Gear 3 Incorrect Ratio

What it means:

  • 3rd gear slip
  • Direct clutch wear typical

Diagnosis:

Fix:

  • Direct clutch rebuild
  • HD upgrade recommended
  • $1,500-3,500

P0734: Gear 4 Incorrect Ratio (Overdrive)

What it means:

  • 4th gear slip
  • OD-specific apply issue

Diagnosis:

  • Pan inspection
  • Specific to OD clutch pack

Fix:

  • OD rebuild
  • $1,500-3,500

P0741: TCC Stuck Off

What it means:

  • TCC commanded on but not engaging
  • Or slipping when commanded

Diagnosis:

Fix:

P0742: TCC Stuck On

What it means:

  • TCC engages and won't release
  • Engine stalls at stop

Diagnosis:

  • TCC solenoid stuck
  • Or apply piston damaged

Fix:

  • Solenoid replacement
  • Or full rebuild if piston damaged

P0748: Force Motor Electrical (PWM Pressure)

What it means:

  • Force motor (line pressure PWM) failure

Diagnosis:

Fix:

  • Force motor replacement: $100-300
  • Or full solenoid pack: $250-450

P0751: Shift Solenoid A Performance

What it means:

  • Shift solenoid A not working correctly

Diagnosis:

  • Resistance test
  • Pressure test for line pressure issue

Fix:

P0753: Shift Solenoid A Electrical

What it means:

  • Electrical fault in shift solenoid A circuit

Diagnosis:

  • Wiring check
  • Solenoid resistance

Fix:

  • Often wiring repair
  • Sometimes solenoid replacement

P0756: Shift Solenoid B Performance

What it means:

  • Shift solenoid B not working correctly

Diagnosis and fix:

  • Same as P0751 for solenoid B

P0758: Shift Solenoid B Electrical

What it means:

  • Electrical fault in shift solenoid B

Fix:

  • Same approach as P0753

P0785: Shift/Timing Solenoid Malfunction

What it means:

  • 3-2 shift solenoid issue

Fix:

  • Solenoid pack replacement typical

P0815: Up Shift Switch

What it means:

  • Driver-input switch fault

Fix:

  • Often button on shift handle
  • Wiring check

P0860: Gear Shift Module Communication

What it means:

  • TCM communication issue

Diagnosis:

  • More serious
  • Check TCM connections
  • Possible TCM replacement

P1810: TFP Valve Position Switch

What it means:

  • Pressure switch manifold issue
  • Specific to 4L80E

Diagnosis:

  • Check PSM
  • Often inside trans pack

Fix:

  • PSM replacement
  • Or full pack: $250-500

P1860: TCC PWM Solenoid Electrical

What it means:

  • TCC PWM circuit issue

Fix:

P1870: TCC Slip Excessive

What it means:

  • TCC slipping (very common)

Diagnosis:

Fix:

  • Solenoid first (cheaper try)
  • Then rebuild with HD apply piston

Multi-code scenarios

Multiple shift solenoid codes:

Multiple gear ratio codes:

Speed sensor + gear codes:

  • Sensor issue causing gear codes
  • Fix sensor first

TCC codes + pressure switch:

  • Internal pressure issue
  • Pack-level service

When NOT to just clear codes

Don't clear if:

  • Haven't fixed underlying issue
  • Code returns immediately
  • Pan shows damage

Read our transmission warning signs

Cost summary

Easy fixes ($50-300):

  • Single sensor replacement
  • Wiring repair
  • Connector cleaning

Medium fixes ($200-800):

Expensive fixes ($1,500-3,500):

  • Full rebuild
  • Multiple clutch packs
  • Hard parts replacement

Code priority order

Address first:

  • Speed sensors (cheap, common)
  • Wiring issues
  • Connectors

Then:

  • Single solenoid issues

Then:

  • Pack-wide failures

Then:

  • Internal rebuild needs

Don't skip pan inspection:

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