TIAGO AMT Gasoline DTC Troubleshooting Guide Version: 2.0 Date: 06-06-2016 Author: Sathi/Anupama Page: 221 of 424 Copyright © 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. 70. P1884-04: Reverse Lamp relay open circuit Overview: ISO Code P1884-04 Customer Symptom Reverse lamp not switching ON Fault Effects (On Vehicle) Reverse lamp not switching ON Lamp Status (If Any) Transmission Fault Lamp OFF Fault Detection Condition This fault gets detected after Ignition On when reverse lamp output is commanded OFF and an open circuit is detected. Normal Operating Condition TCU does not detect open circuit Probable Trouble Area Wiring Harness Connections / Reverse lamp relay / TCU Healing Condition 2000 milliseconds after valid detection of healed condition Component Details: Reverse lamp output is a digital output from TCU to EMS which is driven high to turn ON the reverse lamp through a reverse lamp relay. Preliminary Checks: 1) Check for damage/loose fit or back out of pins at TCU 28 pin vehicle connector, Reverse lamp relay and relay box. 2) Check for visible damage to TCU pins. 3) Check correct fitment of ground cable connections on vehicle chassis. Trouble Shooting:- Step Checks IF YES IF NO 1. Is there any rust/oxidation/damage observed on TCU 28 pin vehicle connector Terminals? Clean the Rust or repair or replace Go to Step 2 2. Is there wiring harness electrical continuity between TCU pin 2 to Reverse lamp relay input pin? Also check for any short to battery or ground on pin 2. Go to Step 3 Establish continuity by rectifying harness connections as per the circuit schematic 3. Is ground connection proper on reverse lamp relay input side? Go to Step 4 Establish continuity by rectifying harness connections as per the circuit schematic 4 Check the TCU ignition and power connections on Pins 5, 1 and 3 respectively. Check for ignition pin toggling to 12 V with ignition key On-Off. Connections are OK? Go to Step 5 Establish continuity by rectifying harness connections as per the circuit schematic 5 Replace the Reverse lamp relay, problem persists? Replace the TCU - the following points by referring TCU parameters using TML diagnostic tool before handing over to customer. Check for proper Reverse lamp functioning. Drive the vehicle through all gears in both Automatic and Manual modes Ensure no DTC is active and Transmission Fault Lamp is OFF.
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