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Home >> Volvo >> 1992 >> 960 4D Sedan >> Repair and Diagnosis >> Engine Performance >> System >> Engine Controls - Tests W/Codes >> Fault Code Testing >> Code 5-1-2 >> Diagnostic Procedure
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Diagnostic Procedure

  1. Check MAF sensor signal. Start and warm up engine. Gear selector: neutral, A/C: off, engine warm. Power consumers such as engine coolant fan, heated rear window, etc. should be off. Using scan tool, select Volvo ST symbol to read off load signal. Value should read 2.3-2.4 volts at idle. If okay, go to next step. If not okay, go to step  16 .
  2. Check vacuum hose to pressure regulator. Remove vacuum hose from pressure regulator. Check hose to be sure that it is not blocked by blowing it through. Is hose OK? If yes, go to next step if engine equipped with quick-release coupling. If engine is not equipped with quick-release coupling, go to  4 . If no, check hose and nipple and fix fault.
  3. Connect pressure gauge. Turn ignition off. Fit Pressure Gauge (999 5011) with Nipple (998 9725) and Adapter (999 5479) before use. If draining unit absent, instead of Fitting Nipple (998 9725), fit Hose (999 5116) and Plug (999 5266). Connect Draining Unit (981 2270), (981 2273) and (981 2282) to Nipple (998 9725) on pressure gauge. Set valve on Pressure Gauge (999 5011) to position 3 (valve should point towards Adapter (999 5479). Remove protective cap on valve which is located on fuel manifold. Connect adapter to valve in locked position. Go to step  5 .
  4. Connect pressure gauge. Turn ignition off. Connect Pressure Gauge (999 5011) between fuel lead and manifold. Use Hose (999 5116) and Nipple (999 5431). Plug free end of gauge with Plug (999 5266). Set valve on (999 5011) to position 1 (valve should point towards Hose (999 5116). Go to next step.
  5. Start fuel pump. Turn ignition off. Remove fuse No 23 in fuse box on left side of instrument panel. Remove FP relay in fuse box on left side of instrument panel position 2. Connect a lead between contacts 1 and 2 on relay base. Turn ignition on. Go to next step.
  6. Read off system pressure on pressure gauge. System pressure should read 300 kPa (3.0 kp/cm2) (43.5 psi). If pressure is okay, go to next step. If pressure is low, go to step  14 . If pressure is high, go to step  15 .
  7. Check fuel filter. Clamp together return lead and check if pressure rises. Pressure must not exceed 600 kPa (6.0 kp/cm2) (87.0 psi). Does pressure rise rapidly? If yes, go to next step. If no, install a new fuel filter.
  8. Check pressure regulator, loss of pressure. Connect vacuum pump to pressure regulator. Pump out air from regulator. Check that system pressure at same rate as regulator pressure. 300 kPa - negative pressure = system pressure. Disconnect hose from vacuum pump. System pressure should return to 300 kPa (43.5 psi). If okay, go to next step. If not okay, install new pressure regulator.
  9. Check pressure regulator, increase in pressure. Connect vacuum pump and Manometer (999 5230) to pressure regulator. Check that system pressure rises as same rate as regulator pressure. 300 kPa - negative pressure = system pressure. Disconnect hose from pressure tester. System pressure should return to 300 kPa (43.5 psi). If okay, go to next step. If not okay, install new pressure regulator.
  10. Check residual pressure. Switch off ignition. Remove lead between contacts 1 and 2 on relay base. Replace FP relay. Value should not fall below 200 kPa (29 psi) in less than 20 minutes. If okay, go to next step if engine equipped with quick-release coupling. If engine is not equipped with quick-release coupling, go to step  12 . If not okay, incorrect residual pressure can be due to leaks in injection valves, connectors, FP non-return valve, or hose. Fix as necessary.
  11. Disconnect pressure gauge. Turn ignition off. Start draining unit. Lock adapter (valve closed). Set valve on pressure gauge to mid position. If draining unit is absent, place paper under quick-release coupling to soak up any fuel spillage when pressure gauge is removed. Remove adapter from valve. Stop draining unit. Refit components. Do not forget to refit safety cap to valve. Go to step  13 .
  12. Disconnect pressure gauge. Turn ignition off. Place paper under fuel lead to soak up any fuel spillage when pressure gauge is removed. Remove pressure gauge. Any plastic tape on fuel pipes which is removed must be replaced. Go to next step.
  13. Connect breakout box to ECU. See CONNECTING MEASURING UNIT TO ECU  . Check all signals to ECU. See PIN VOLTAGE CHARTS article. Repair as necessary. Testing is completed.
  14. System pressure too low. Clamp together return lead and check if pressure rises. Pressure must not exceed 600 kPa (6.0 kp/cm2) (87.0 psi). Does pressure rise? If yes, pump and hose is fault-free. Try with a new pressure regulator. Measure system pressure again. Repair is completed. If no, check fuel pump filter. If filter is okay, try with a new fuel pump. Measure system pressure. Testing is completed.
  15. System pressure too high. Remove lead between contacts 1 and 2 on relay base. Remove return hose from pressure regulator. Blow through hose. Is hose okay? If yes, Try with a new pressure regulator. Measure system pressure. Testing is complete. If no, check if return hose is damaged or blocked. Clean and change. Measure system pressure. Testing is complete.
  16. Check MAF sensor ground lead. Turn ignition off. Disconnect MAF sensor. Connect an ohmmeter between MAF sensor connector contact No. 1 and ground. Ohmmeter should read approx. 0 ohms. If okay, check MAF sensor connector for contact resistance and oxidation. Repair as needed. Go to next step. If not okay, go to step  18 .
  17. Check load signal. Start and warm up engine. Gear selector: neutral, A/C: off, engine warm. Ensure engine coolant fan, heated rear window, etc. are off. Using scan tool, select Volvo ST symbol to read off load signal. Value should read 2.3-2.4 V at idle. If okay, testing is complete. If not okay, install new MAF and retest. Testing is complete.
  18. Check connector. Disconnect MAF sensor connector. Check 53-pin connector in left wheel-arch (C131) connector 15 for contact resistance and oxidation. Repair as needed. Ensure ECU is connected. Connect an ohmmeter between MAF sensor connector contact No. 1 and ground. Ohmmeter should read approx. 0 ohms. If okay, source of DTC is bad contact in connector. If not okay, check lead between MAF sensor connector contact No. 1 and control point on engine (31/33) for open. Go to next step.
  19. Check load signal. Start and warm up engine. Gear selector: neutral, A/C: off, engine warm. Ensure engine coolant fan, heated rear window, etc. are off. Using scan tool, select Volvo ST symbol to read off load signal. Value should read 2.3-2.4 V at idle. If okay, testing is complete. If not okay, install new MAF and retest. Testing is complete.
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