TIAGO

TIAGO AMT Gasoline

DTC Troubleshooting Guide

Version: 2.0

Date: 06-06-2016

Author: Sathi/Anupama

Page: 107 of 424

TATA MOTORS Ltd.

This document must not be used in any way, such as copying and redistributing to third parties, without the consent of author.

32.

P0725-02: Engine Speed Input Circuit Signal not valid

Overview:

ISO Code

P0725-02

Customer Symptom

Transmission Fault Lamp ON

Vehicle not picking up

Transmission going automatically to neutral from gear when

coming to halt after drive.

Gear shift request by lever disabled.

no gearshifts

Fault Effects (On Vehicle)

Transmission Fault Lamp ON,

Vehicle not picking up,

Transmission going automatically to neutral from gear when

coming to halt after drive.

Gear shift request by lever disabled,

no gearshifts

Lamp Status (If Any)

Transmission Fault Lamp ON

Fault Detection Condition

This fault gets detected after Ignition On if the engine speed is

sent with invalidity flag set by EMS over CAN

Normal Operating Condition

engine speed is sent as valid by EMS over CAN

Probable Trouble Area

Wiring Harness Connections / EMS / TCU

Healing Condition

200 milliseconds after valid sensor signal

Component Details:

Engine Speed signal is transmitted via CAN bus to the TCU.

Preliminary Checks:

1) Loose/ Damaged Crank sensor Connections.

2) Check for damage or back out of pins at EMS connector and TCU connector.

3) Check correct fitment of ground cable connections on vehicle chassis.

Trouble Shooting:-

Step Checks

IF YES

IF NO

Is there any rust/oxidation/pin backout

observed on EMS or TCU connectors?

Clean the Rust or repair or

replace

Go to Step 2

Check wiring harness electrical continuity

between TCU pins 28 and 25 to EMS

connector pins 144 and 132 respectively, Also

check resistance between TCU pins 28 and

connected.(should be close to 60 ohm). Are

both these checks OK?

Go to Step 3

Establish continuity by

rectifying harness

connections as per the

circuit schematic

Diagnose the crank sensor input to EMS

(Refer EMS service manual), is there a

problem with crank sensor or crank sensor to

EMS connection?

Ensure correct connection of

crank input to EMS as per

EMS service manual.

Go to step 4

Is TCU power connections on TCU connector

pins 5, 1, 3? Specifically check Ignition supply

toggling with key on/off.

Go to Step 5

Check and rectify

harness ground and

power connections.

Connect the EMS diagnostic tool and check

the value of engine speed with engine ON, is

correct value observed?

Replace the TCU

Recheck EMS crank

speed sensor

connections