TATA BSVI Gasoline_Bifuel Program – EMS ECU Bosch DTC Troubleshooting Service Manual Version: 1.9 Date: 24-01-2022 Prepared By: Veer K. Singh / Prudhvi B Varma Checked By: Yeshwant Jadhav Approved By: Sanjeev M. Document Part No: 2921 02 xxx xxxx Page: 1454 of 1692 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. P0191-85: Rail pressure Exceeds (Maximum Threshold) - CNG System pressure too High Overview: ISO Code P0191-85 Customer Symptom If running in CNG, fuel mode switch to gasoline Fault Effects (On Vehicle) If running in CNG, fuel mode switch to gasoline Lamp Status (If Any) MIL ON after 3 drive cycle Fault Detection Condition This fault gets logged when CNG rail pressure above max. threshold. Normal Operating Condition Fuel mode changeover as per selection, CNG rail pressure is within range Probable Trouble Area CNG fuel rail, CNG pressure regulator, CNG PT sensor and EMS ECU Healing Condition After 3 drive cycles Fault present deletion 1. Clear DTC Command form Scan tool. 2. Stack Over Flow. 3. 40 warm up cycles. 4. ECU flashing 5. ECU power fail Component Details: The CNG rail pressure and temperature sensor is a solid state pressure transducer having a NTC thermistor for measuring pressure and temperature of CNG. The pressure sensor is a semiconductor that varies electrical resistance when pressure is applied to its silicon chip. This sensor outputs the voltage in proportion to the internal fuel pressure. CNG Tank Pressure sensor measures CNG pressure in CNG storage tank and high pressure line. It is located before CNG regulator valve. CNG Shut off Valve Pressure Regulator is opened to allow supply of CNG from high pressure line to low pressure line whenever CNG fuel mode is active. Preliminary Checks: 1) Loose/ Damaged Connections between Sensors/actuators and EMS ECU. 2) Check for back out of pins at both Sensors/actuators connector and ECU connector. 3) Check for damage of pins at both Sensors/actuators connector and ECU connector. 4) Check the continuity from Sensors/actuators connector pins to the ECU pins.
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