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Transmission/Transfer Case 5-119
®
05745159
DTC P1871 Undefined Gear Ratio
Circuit Description
The PCM calculates ratio based on transmission input and out- This DTC detects an unknown ratio.
Conditions For Seating The DTC
The following conditions are met for 10 seconds. • No DTCs P0121, P0122, P0123, P0220, P0221, P0222, P0223, P0225, P0226, P0227, P0228. • No DTCs P0716 or P0717. • No DTCs P0722 or P0723. • No DTCs P1810. • No Four Wheel Drive Lo DTC P1875. • Four Wheel Drive Lo fail counters are clear. • Vehicle Speed is greater than 11 km/h (7 mph). • Throttle angle is greater than 25%. • Transmission fluid temperature is greater than 20°C (68°F). • 4.5 seconds since last gear change. • Engine Speed is greater than 3650 rpm. • Engine Torque is between 80 and 450 ft/ lbs. • Gear Ratio is greater than 2.63 or less than 0.70 • Above conditions occur for 10 seconds.
Action Taken When The DTC Sets
• The PCM will command maximum line pressure. • The PCM will freeze shift adapts.
Conditions For Clearing The MIL/DTC
• The PCM will turn the warning lamp off after three con- secutive ignition cycles without a failure reported. • The DTC can be cleared using the scan tool. • The PCM will cancel the DTC default actions when a fault no longer exists, and the ignition is cycled “Off”
Diagnostic Aids
• Inspect the wiring for poor electrical connection at the PCM and the transmission 20-way connector. • When diagnosing for a possible intermittent short or open condition, move or wiggle the wiring harness • If any engine DTC(s) or TP Sensor codes are present in memory, diagnose and clear the engine DTC(s) first.
Test Description
The numbers below refer to the diagnostic table. 1. This test checks indicated range signal to the actual selected range. A faulty switch could set pressure 2. This test checks for proper ratios when in each com- manded gear state. TRANS RANGE C IINPUT TRANS RANGE B INPUT TRANS RANGE A INPUT C34 P R N D E C REV SWITCH LO SWITCH D2 SWITCH D3 SWITCH D4 SWITCH C32-S C32-H C32-K 764 PP 763 DB 762 OR C29-B4 C29-B5 C29-B6 A / T ISS HIGH A / T ISS LOW B C32-B A A AUTO TRANS SPEED SENSOR A/T ISS C27-D1 C27-D11 495 DB 496 GY POWERTRAIN CONTROL MODULE (PCM) 9-S12-071.1 VSS VSS T W I S T E D PA I R B A TRANFER CASE VEHICLE SPEED SENSOR VSS C29-A6 C29-A3 679 LG 676 PP T W I S T E D PA I R DIGITAL RATIO ADAPTER AUTOMATIC TRANSMISSION 223 DB 565 BR C33-B A |