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Home >> Volvo >> 1998 >> S70 GLT >> Repair and Diagnosis >> Engine Performance >> System >> Engine Controls - Tests W/Codes >> Diagnostic Tests >> DTC P0115/EFI 123, DTC P0116/EFI 123, DTC P0117/EFI 123 & DTC P0118/EFI 123 >> Diagnosis (Signal Too Low)

Diagnosis (Signal Too Low)

WARNING: Before beginning testing, disconnect engine cooling fan relay harness connector "A", to ensure cooling fan will not run. DTC P1619/EFI 514 may be stored. After fault-tracing, harness connector must be reconnected.
NOTE: ECM terminal A18 is a common ground for ECT sensor, Camshaft Position (CMP) sensor, and Throttle Position (TP) sensor.
  1. Connect scan tool. See RETRIEVING & ERASING DTCs  under SELF-DIAGNOSTIC SYSTEM. If no DTC's are stored, go to next step. If DTC P0120/EFI 411, DTC P0122/EFI 411, DTC P0123/EFI 411 or DTC P0340/EFI 314 are stored, check for contact resistance and oxidation at ECM terminal A18. Repair as necessary. After repairs, repeat step.
  2. If signal is PERMANENT go to next step. If signal is INTERMITTENT, check for intermittent short to ground in circuit between ECT sensor harness connector terminal No. 1 and ECM terminal A31. Repair as necessary. After repairs, go to step  4.
  3. Disconnect ECT sensor harness connector. Turn ignition on. Using scan tool in DIAGNOSTIC MODE, scroll through values list. Read voltage for ECT sensor. Voltage should be approximately 5 volts. If voltage is within specification, replace ECT sensor. After repairs, go to next step. If voltage is not within specification, check for short to ground in circuit between ECT sensor harness connector terminal No. 1 and ECM terminal A31. Repair as necessary. After repairs, go to next step.
    4. NOTE: Use of external infrared thermometer can be used to monitor engine coolant temperature in place of Volvo temperature box (999 5281) and Volvo temperature sensor (999 5282).
  4. Turn ignition off. Reconnect all connectors and components. Connect DVOM with Volvo temperature box (999 5281) and Volvo temperature sensor (999 5282). Carefully remove expansion tank cap. Clamp hose between radiator and thermostat. Disconnect hose from thermostat housing. Insert sensor in thermostat housing and reinstall hose. Remove hose clamp. Start engine and warm until thermostat is open. Using scan tool in DIAGNOSTIC MODE, read ECT sensor. If ECT sensor is within specification, fault was corrected. If reading is not within specification, repeat test starting with step  1.
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