Allison 3000 & 4000 Gen 4 Fault Code: P071D General Purpose Input Fault

DIAGNOSTIC RESPONSE:
None

CIRCUIT DESCRIPTION:
Some emergency vehicles are equipped with an input function known as Auxiliary Function Range Inhibit (AFRI) (Special), which prevents inadvertent range selection when auxiliary equipment is operating.

This function is enabled under the following conditions:
1. Input wire 101 is connected to signal return wire 103 and,
2. Input wire 142 is connected to battery ground.

In a typical installation, a dash-mounted auxiliary equipment selector switch completes the circuit between wires 101 and 103. A second switch closes during operation of the auxiliary equipment to complete the circuit between wire 142 and battery ground. Both switches must be closed for the function to be enabled. When the two input wires (101 and 142) are ON, the TCM inhibits all Neutral-to-Range shifts. The inhibit remains in effect until either one of the two input wires changes state to OFF, or transmission output speed exceeds a preset value. The TCM sets P071D if it detects that the two input wires are in two different states (ON or OFF) for longer than 120 seconds.

The AFRI (Special) service indicator is available via a datalink message or an analog signal. Select the appropriate schematic for the wire number specified in the TCM calibration. Also refer to the OEM Technician Library for additional information.

Wiring Schematics for Input F: AFRI (Special):
Type of Activation: Switch
Product Family: 3000/4000
Function I.D.: F
Wire Assignment: 101, 142, 113

Type of Activation: Switch
Product Family: 3000/4000
Function I.D.: F
Wire Assignment: 101, 142, 113

Type of Activation: Switch w/service indicator on SAE J1939
Product Family: 3000/4000
Function I.D.: F
Wire Assignment: 101, 142

CONDITIONS FOR RUNNING THE DTC:
1. TCM is calibrated to receive the AFRI (Special) inputs.
2. After TCM initializes normally and engine speed is above 200 rpm for more than 5 seconds, this DTC test will run at 1 second intervals.

CONDITIONS FOR SETTING THE DTC:
Function input wire states (ON or OFF) on W101 and W142 do not match longer than 2 minutes.

ACTION TAKEN WHEN THE DTC SETS:
When DTC P071 Dis active, the following conditions occur:
1. The DTC is stored in the TCM history.
2. The TCM illuminates the CHECK TRANS light.
3. TCM inhibits AFRI (Special) operation allowing transmission to make range shifts from Neutral (N).

CONDITIONS FOR CLEARING THE DTC/CHECK TRANS LIGHT:
The diagnostic tool may be used to clear the DTC from the TCM history. The TCM automatically clears the DTC from the TCM history if the vehicle completes 40 warm-up cycles without the DTC recurring.

DIAGNOSTIC AIDS:
AFRI (Special) functionality may be checked by installing jumpers for W101 and W142 in place of Original Equipment Manufacturer (OEM) input wires. With brake applied, select D (Drive) and then switch input jumpers to a known good vehicle ground. Transmission should shift to Neutral (N) if TCM and programming are OK. If TCM CIN and wire package are correct, but AFRI (Special) is inhibited with active code, then change TCM with known good TCM and recheck.

This DTC may be caused by:
1. Short to power or short to another wire in either W101 or W142.
2. High resistance or open in either W101 or W142.
3. Poor vehicle grounds.
4. Unlocked connectors, expanded terminals, poor pin crimps or unlocked pins causing high resistance or open circuit.
5. Unlocked connectors, unlocked pins, causing shorts in connectors.
6. AFRI (Special) enabled in TCM programming in error.
7. TCM ground is at different voltage potential than the ground of the OEM voltage source responsible for switching GPI circuit controlling AFRI (Special).
8. Defective TCM.