850 (Temperature Gauge Does Not Work At All)
- Turn ignition on. Activate diagnostic test mode No. 3. See DIAGNOSTIC TEST MODE NO. 3 under SELF-DIAGNOSTICS. Check if temperature gauge needle is at edge of Red section. If temperature gauge does not operate as specified, replace instrument cluster.
- If temperature gauge needle is at edge of Red section, there is a possibility a fault exists between sensor and fuel system ECU, between fuel system ECU and ignition system ECU, or between ignition system ECU and instrument cluster. See Fig 1. Ensure testing is performed in correct sequence as a fault between sensor and fuel system ECU may cause faults in all 3 ECUs.
Courtesy of VOLVO CARS OF NORTH AMERICA.
- Start testing by checking whether fuel system ECU exhibits Code 1-2-3 in diagnostic test mode No. 1 on diagnostic output A2. See appropriate TESTS W/CODES
article in ENGINE PERFORMANCE and diagnose Code 1-2-3 as necessary.
- If fuel system ECU does not exhibit Code 1-2-3, check whether ignition system ECU exhibits Code 1-2-3 in diagnostic test mode No. 1 on diagnostic output A6. See appropriate TESTS W/CODES
article in ENGINE PERFORMANCE and diagnose Code 1-2-3 as necessary.
- If ignition ECU exhibits Code 1-2-3, there is no temperature signal going to ignition ECU or it is shorted to ground, voltage, or both. See appropriate TESTS W/CODES
article in ENGINE PERFORMANCE. If ignition ECU does not exhibit Code 1-2-3, check for an open circuit in temperature signal Green/Gray wire between instrument cluster 30-pin connector terminal A26 and ignition ECU connector terminal B23.