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Home >> Volvo >> 1998 >> S70 Base, Standard >> Repair and Diagnosis >> Engine Performance >> System >> Engine Controls - Tests W/Codes >> Diagnostic Tests >> DTC P0170/EFI 231-EFI 232, DTC P0171/EFI 231-EFI 232 & DTC P0172/EFI 231-EFI 232 >> Diagnosis (Lower Limit)

Diagnosis (Lower Limit)

  1. Check for other DTCs. If DTC P0440/EFI 315 is stored, perform testing on that DTC first. If DTC 315 is not stored, go to next step.
  2. Turn ignition on, with engine off. Ignition off. Connect mass air flow (MAF) sensor. Turn ignition on. Connect a voltmeter between Mass Air Flow (MAF) sensor connector terminals 2 and 4. The voltmeter should display 0.1-0.2 volt. If voltage is 0.1-0.2 volt, go to step  3. If voltage is not 0.1-0.2 volt, retest using new MAF sensor.
  3. Check for air leakage in the exhaust sytem. See EXHAUST SYSTEM in SYSTEM/COMPONENT TESTS article. If there are no exhaust air leaks, go to step  4. If there are any exhaust air leaks, repair as necessary. After repairs, erase any stored DTCs.
  4. Check fuel pressure and residual fuel pressure. See FUEL SYSTEM in BASIC TESTING article. If fuel pressure is OK, go to step  5. If fuel pressure is NOT OK, repair fuel system as necessary. After repairs, erase any stored DTCs.
  5. Checking canister purge valve. Remove hose to intake manifold from canister purge valve. Reinstall hose after fault-tracing. When installing use a new hose clamp. Connect vacuum pump to canister purge valve connector. Pump up a vacuum. The vacuum gauge should indicate a steady vacuum. If reading is OK, go to step  6. If reading is incorrect, try a new canister purge valve. Erase any stored DTCs. Reset long-term fuel trim.
  6. Checking engine oil level Check engine oil level. The oil level should be between the MIN and MAX marks. Fill oil to correct level. Go to step  7.
  7. Checking engine oil. Start the engine and idle it for a few minutes. Use scan tool to read off and note the value of the short-term fuel trim. Disconnect and plug crankcase ventilation. Read off the short-term fuel trim value again. This value should be more or less the same. If value is OK, go to step  8. If reading is incorrect, this indicates that the engine oil is contaminated with fuel. Change engine oil and oil filter. Erase any stored DTCs. Reset long-term fuel trim.
  8. Connect test (breakout) box to ECM and check ground connections. See COMPUTERIZED ENGINE CONTROLS in SYSTEM/COMPONENT TESTS article. Reconnect ECM. Repair as necessary. Go to step  9.
  9. Verification. After carrying out the repair, check that the fault has been remedied. Turn ignition off. Reconnect connectors and reinstall components. Use the scan tool to read off the value of long-term fuel trim. Test drive the car. Watch the long-term fuel trim value until it switches to completed. If DTC EFI-231/232 is stored it should have intermittent status.
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