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This instruction show you guide on how to solve Allison 3000 & 4000 Gen5 transmission P071A neutral at stop input failed ON.
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Inhibit Neutral at Stop operation
CIRCUIT DESCRIPITION
When Function AS:
Neutral at Stop is active,the Transmission Control Module(TCM) automatically commands transmission operation at a reduced load state similar to Neutral (N).The purpose of the function is to reduce the load on the engine when the vehicle is stop which improves fuel economy and also reduces heat load of the transmission in high start/stop duty cycles.To activate Neutral at Stop,the vehicle must be in first rang,at a stop,service brakes applied,accelerator pedal approximately at 0% and the TCM GPI terminal for Neutral Stop must see V+,V Ign,or V Bat.
Neutral at Stop deactivates when the service brake is released.Supplemental controls such as a door switch or Neutral at Stop enable dash switch may be wired in series with the service brake pressure switch; alternately, a vehicle Programmable Logic Controller (PLC) output may switch the Neutral at Stop signal as a result of a service brake pressure switch input to the PLC. The signal used to activate Neutral at Stop may be on W102, W123 or W143, depending upon which Input/Output (I/O) package was selected in the TCM calibration.Neutral at Stop typically uses a switch-to-battery input (analog). Refer to the OEM Technician’s Library for Neutral at status is in a stuck “ON” or “OFF” state.
Neutral at Stop:
GPI#:1
GPI Type: +
TCM Pin Number 23
Wire Number: 123
Wire Color: Green
Termination Point(s): Service Brake Press
ire Switch to V+ or PLC Output
GPI#:2
GPI Type: +
TCM Pin Number: 2
Wire Number: 102
Wire Color: Yellow
Termination Point(s: Service Brake Pressure Switch to V+ or PLCutput
GPI#:3
GPI Type: +
TCM Pin Number:43
Wire Number: 143
Wire Color: Blue
Termination Point(s: Service Brake Pressure Switch to V+ or PLC Output
ACTION TAKEN WHEN THE DTC SETS:
When DTCP071A is active,the following conditions occur
1 The DTC is stored in the TCM history.
2 The TCM does note illuminate the CHECK TRANS light.
3 TCM inhibits Neutral at Stop operation.
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 completes40 warm-up cycles without the DTC recurring.
DIAGNOSTIC AIDS:
This DTC may be caused by:
1 Short to power or short to another wire for the GPI circuit con trolling Neutral at Stop feature:e.W102,W123,or W143.
2 Service brake integrations: defective switch or incorrect wiring; e.g.,, pressure switches are closed when they should be open. If Neutral at Stop enable switch or door switch is integrated in series, all switches would need to be stuck closed or wired on the wrong side side versus normally open side.
3 PLC Neutral at Stop integrations: a miswired, misprogrammed,or defective circuit from PLC controlling the TCM GPI signal for Neutral at Stop that is maintaining circuit above 3.4 volts with service brakes released.
4 Neutral at Stop enabled in TCM programming error.
5 TCM ground is at different voltage potential than the ground of the OEM voltage source responsible for switching GPI circuit controlling Neutral at Stop;e.g.PLC,vehicle ignition,body controller,et.
6 Defective TCM.
More Allison repair case,please refer to Allison Trouble Repair
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