Home/Chevrolet/C3500 HD/Chevrolet C3500 HD (1991-2000)/Repair manual/Engine Controls - Tests W/codes - 7.4l/CODE 68, OVERDRIVE RATIO ERROR - 4L80-E TRANSMISSION

Contents

Section: Engine Controls - Tests W/codes - 7.4l

MODEL IDENTIFICATION

INTRODUCTION

TERMINOLOGY

SELF-DIAGNOSTIC SYSTEM

HARD FAILURES

INTERMITTENT FAILURES

DIAGNOSTIC PROCEDURE

RETRIEVING CODES (NON-SCAN)

READING TROUBLE CODES

CLEARING TROUBLE CODES

ECM LOCATION

Diagnostic Aids

Field Service Mode Check

SPECIAL TOOLS (DIAGNOSTIC)

SCAN TESTER USAGE

SCAN TESTER DATA

TROUBLE CODE CHARTS

CODE 13, OPEN OXYGEN SENSOR CIRCUIT

CODE 14, COOLANT SENSOR SIGNAL VOLTAGE LOW

CODE 15, COOLANT SENSOR SIGNAL VOLTAGE HIGH

CODE 16, VSS BUFFER FAULT

CODE 21, TPS SIGNAL VOLTAGE HIGH

CODE 22, TPS SIGNAL VOLTAGE LOW

CODE 24, VEHICLE SPEED SENSOR - "C" & "K" SERIES

CODE 24, VSS TRANSMISSION OUTPUT SIGNAL - A/T

CODE 28, TRANSMISSION RANGE PRESSURE SWITCH

CODE 32, EGR CIRCUIT ERROR BACKPRESSURE EGR WITH SOL

CODE 32, EGR CIRCUIT ERROR WITH EVRV SOLENOID

CODE 32, EGR CIRCUIT ERROR - "P" SERIES WITH LINEAR EGR

CODE 32, EGR CIRCUIT ERROR - SERIES W/ LINEAR EGR

CODE 33, MAP SENSOR SIGNAL VOLTAGE HIGH

CODE 34, MAP SENSOR SIGNAL VOLTAGE LOW

CODE 35, IDLE SPEED ERROR

IAC Valve Reset Procedure

System Too Lean

System Too Rich

Throttle Body

IAC Valve Connections

PCV Valve

CODE 36, IDLE SPEED ACTUATOR FAULT - A/T

CODES 37/38, TCC BRAKE SWITCH ON/OFF

CODE 39, TCC STUCK OFF - 4L80-E TRANSMISSION

CODE 42, IGNITION CONTROL

CODE 43, KNOCK SENSOR WITHOUT SPARK MODULE (DUAL SENSORS)

CODE 43, KNOCK SENSOR WITHOUT SPARK MODULE (SINGLE SENSOR)

CODE 43, KNOCK SENSOR WITH SPARK CONTROL MODULE

CODE 44, LEAN EXHAUST INDICATION

O2 Sensor Wire

Fuel Contamination

Fuel Pressure

Exhaust Leaks

CODE 45, RICH EXHAUST INDICATION

Fuel Pressure High

Ignition Ground

Fuel Canister

MAP Sensor

TPS

O2 Sensor Contamination

EGR Problem

CODE 51, PROM ERROR (FAULTY OR INCORRECT PROM)

CODE 52, FAULTY CALPAK

CODE 52/53, SYSTEM VOLTAGE HIGH

CODE 55, ECM/PCM ERROR

CODE 54, FUEL PUMP CIRCUIT

CODE 58, TRANSMISSION FLUID TEMPERATURE HIGH

CODE 59, TRANSMISSION FLUID TEMPERATURE LOW

CODE 66, 3-2 CONTROL SOLENOID CKT FAULT 4L60-E TRANSMISSION

CODE 67, TCC SOLENOID CIRCUIT CHECK - 4L60-E TRANSMISSION

CODE 68, OVERDRIVE RATIO ERROR - 4L80-E TRANSMISSION

CODE 69, TORQUE CONVERTER CLUTCH STUCK ON 4L60-E TRANSMISSION

CODE 69, TORQUE CONVERTER CLUTCH STUCK ON 4L80-E TRANSMISSION

CODE 72, VSS CIRCUIT LOSS TRANSMISSION OUTPUT SIGNAL

CODE 73, PRESSURE CONTROL SOLENOID (CURRENT ERROR)

CODE 74, TRANSMISSION INPUT SPEED ERROR 4L80-E TRANSMISSION

CODE 75, SYSTEM VOLTAGE LOW

CODE 79, TRANSMISSION FLUID TEMPERATURE HIGH

CODE 81, TRANSMISSION 2-3 ERROR

CODE 82, TRANSMISSION 1-2 ERROR

CODE 83, TCC SOLENOID CIRCUIT FAULT

CODE 85, UNDEFINED GEAR RATIO

CODE 86, LOW GEAR RATIO ERROR

CODE 87, HIGH GEAR RATIO ERROR

SUMMARY

All sections

CODE 68, OVERDRIVE RATIO ERROR - 4L80-E TRANSMISSION Chevrolet C3500 HD

Engine Controls - Tests W/codes - 7.4l 1 illustration ~120 words

CODE 68, OVERDRIVE RATIO ERROR - 4L80-E TRANSMISSION

Control module monitors the difference in engine RPM and input shaft RPM. With transmission in Drive, scan tester reading should show engine speed closely matching input speed.

Note. Test numbers refer to numbers on diagnostic chart.

Checks indicated range signal to selected range. A faulty switch could set this code.
Checks TCC for slippage while in a commanded lock-up state.

Check for spread connectors at pass-thru connector. Code 68 will set when going to default (2nd gear). If code is intermittent, see INTERMITTENTS in TESTS W/O CODES - GASOLINE article.

Code 68 Flow Chart (All Models) Overdrive Ratio Error - 4L80-E Transmission. Scheme 246

Scheme 246: Code 68 Flow Chart (All Models) Overdrive Ratio Error - 4L80-E Transmission

Scheme 246: Code 68 Flow Chart (All Models) Overdrive Ratio Error - 4L80-E Transmission