Allison 3000 & 4000 Gen 5 Engine Speed Sensor Circuit No Signal Solution

Here is the instruction show you guide on how to solve engine speed sensor circuit No signal error for Allsion 3000& 4000 Gen 5.

Related Contents:

2025 2019 Allison DOC Transmission Diagnostic Software Free Download

NEXIQ USB Link 3

 

DIAGNOSTIC RESPONSE:

Default to turbine speed

 

CIRCUIT DESCRIPTION:

The speed sensors are devices which convert mechanical motion to an electrical signal. This test detects whether out put speed is unreasonably low.

 

ACTION TAKEN WHEN THE DTC SETS:

When DTC P0727 is active,the following conditions occur:

 

1 DTC PO727 is stored in the TCM history.

2 The TCM does not illuminate the CHECK TRANS light.

3 If ignition is OFF,then engine speed is set to 0.If turbine shaft speed is greater than the engine speed calibration default value,then substitube turbine shaft speed as engine speed.

 

CONDITIONS FOR CLEARING THE DTC/CHECK TRANS LIGHT:

Use the diagnostic tool 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:

DTC P0727 may be caused by:

1 W139 and/or W159 shorted to another wire in chassis harness or to ground.

2 W139 and/or W159 high resistance or open circuit.

3 Broken or defective connector assemblies allowing pushed back pins to short together.

4 Unlocked connectors,missing seal plugs allowing moisture in connectors.

5 Fatigued wires at speed sensor connectors (broken strands).

6 Incorrect pin crimps or expanded terminals.

7 Defective engine speed sensor.

8 Defective TCM.

9 Wire pair not twisted or not sufficiently twisted.

 

NOTE: Inspect that the speed sensor wiring consists of twisted pairs at the rate of 12 to 16 twists per 300 mm. These twists must extend the entire length of the wiring harness to within at least 50 mm of the speed sensor connector.

 

Review applicable information in control system and transmission specifications to find additional circuit specifications,system and connector diagrams and troubleshooting tips.

 

More Allison repair case,please refer to Allison Trouble Repair