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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 High)

Diagnosis (Signal Too High)

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. On scan tool, if signal is PERMANENT, go to step  3. If signal is INTERMITTENT, check for loose connections at ECT sensor and ECM harness connectors. Repair as necessary. Check for an intermittent open and/or short to voltage in circuit between ECT sensor harness connector terminal No. 1 and ECM terminal A31. Repair as necessary. Check for intermittent open in circuit between ECT sensor harness connector terminal No. 2 and ECM terminal A18. Repair as necessary. After repairs, go to step  9.
    3. WARNING: If cooling fan continues operating after engine has been turned off, cooling fan must be allowed to stop before resistance is measured.
  3. Turn ignition off. Wait approximately 3 minutes. Disconnect ECT sensor harness connector. Using DVOM, measure resistance between ground and ECT sensor harness connector terminal No. 2. Resistance should be approximately zero ohms. If resistance is within specification, go to next step. If resistance is not within specification, go to step  6.
  4. Turn ignition on. Using DVOM, measure voltage between ECT sensor harness connector terminals No. 1 and No. 2. Voltage should be approximately 5 volts. If voltage is more than specified, go to next step. If voltage is within specification, go to step  7. If voltage is less than specified, go to step  8.
    5. NOTE: ECT sensor may malfunction if there is short to voltage in signal circuit.
  5. Check for short to voltage in circuit between ECT sensor harness connector terminal No. 1 and ECM terminal A31. Turn ignition off. Using DVOM, measure resistance between ECT sensor harness connector terminals No. 1 and No. 2. Resistance should be approximately 2,200 ohms at 77°F (25°C). See Fig 1. If resistance is within specification, ECT sensor is okay. Go to step  9. If resistance is not within specification, replace ECT sensor. After repairs, go to step  9.
  6. Turn ignition off. Check for contact resistance and oxidation at ECM harness connector. Repair as necessary. Ensure ECM is securely connected. Using DVOM, check resistance between ground and ECT sensor harness connector terminal No. 2. Resistance should be approximately zero ohms. If resistance is within specification, DTC was caused by loose connections in ECM harness connector. Go to step  9. If resistance is not within specification, check for an open in circuit between ECT sensor harness connector terminal No. 2 and ECM terminal A18. Repair as necessary. After repairs, go to step  9.
  7. Turn ignition off. Using DVOM, check resistance between ECT sensor harness connector terminals No. 1 and No. 2. Resistance should be approximately 2,200 ohms at 77° F (25° C). See Fig 1. If resistance is within specification, check for contact resistance and oxidation at ECT sensor harness connector. Repair as necessary. After repairs, go to step  9. If resistance is not within specification, replace ECT sensor. After repairs, go to step  9.
  8. Turn ignition off. Check for contact resistance and oxidation at ECM harness connector. Ensure ECM is securely connected. Turn ignition on. Using DVOM, measure voltage between ECT sensor harness connectors No. 1 and No. 2. Voltage should be approximately 5 volts. If voltage is within specification, DTC was caused by loose connections in ECM harness connector. Go to next step. If voltage is not within specification, check for an open in circuit between ECT sensor harness connector terminal No. 1 and ECM terminal A31. Repair as necessary. After repairs, go to next step.
    9. 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).
  9. 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.
Fig 1: ECT Temperature Vrs. Resistance Specification Chart
G00308186Courtesy of VOLVO CARS OF NORTH AMERICA.
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