H8 LOCATE THE VACUUM LEAK
NOTICE

o not clamp or pinch a hard plastic hose. Use a vacuum cap or equivalent to restrict the hose.
Note:Restricting the EVAP vapor hose while the EVAP emission canister is purging may shift the SHRTFT. Carry out a visual inspection as necessary.
Note:When monitoring for a decrease in the SHRTFT PIDs in the following steps, if SHRTFT1 equals +15% and the hose is restricted, SHRTFT1 decreases to -7%. The total decrease in the SHRTFT PIDs equals 22%.
- Locate the vacuum tees for the intake air and PCV systems.
- Ignition ON, engine running.
- Access the PCM and monitor the SHRTFT1 (PER) and SHRTFT2 (PER) PIDs.
- Restrict the vacuum lines one at a time for 30 seconds. If a vacuum leak is present, the SHRTFT PID values decrease as the hose is restricted.
Is the decrease in the SHRTFT PIDs greater than 15 percent when one of the vacuum hoses is restricted?
Yes
- GO to H9
.
No
- INSPECT the intake air system for a vacuum leak in the intake manifold or intake gaskets. REPAIR as necessary.
- For repair verification, GO to H9
.
H9 VACUUM LEAK REPAIR VERIFICATION
Note:If the freeze frame ECT PID is available, stabilize the engine at the temperature recorded by the freeze frame ECT PID. If the freeze frame ECT PID is not available, maintain the engine coolant temperature between 82°C - 101°C (180°F - 215°F) and the intake air temperature less than 46°C (115°F).
- Ignition ON, engine running.
- Access the PCM and monitor the SHRTFT1 (PER) and SHRTFT2 (PER) PIDs.
- Allow the engine to stabilize at the temperature necessary to recreate the concern.
- Record the SHRTFT1 and SHRTFT2 PID values.
- Ignition OFF.
- Repair the vacuum leak.
- Ignition ON, engine running.
- Allow the engine to stabilize at the temperature necessary to recreate the concern.
- Compare the recorded SHRTFT PID values, prior to the vacuum leak repair, to the current SHRTFT PID values.
Is the decrease in the SHRTFT PIDs greater than 15 percent?
Yes
- RESET the keep alive memory (KAM). REFER to Section 2, Resetting The Keep Alive Memory (KAM) See: Computers and Control Systems > Diagnostic Trouble Code Tests and Associated Procedures > Resetting The Keep Alive Memory (KAM). REPEAT the self-test.
No
- A vacuum leak is still present.
- GO to H8
.
H10 CHECK THE UO2SPC CIRCUIT FOR AN OPEN
Note:Only the suspect universal HO2S needs to be diagnosed.
- Ignition OFF.
- Universal HO2S connector disconnected.
- PCM connector disconnected.
- Measure the resistance between:
image
Is the resistance less than 5 ohms?
Yes
- GO to H11
.
No
- REPAIR the open circuit.
- RESET the keep alive memory (KAM). REFER to Section 2, Resetting The Keep Alive Memory (KAM) See: Computers and Control Systems > Diagnostic Trouble Code Tests and Associated Procedures > Resetting The Keep Alive Memory (KAM). REPEAT the self-test.
H11 CHECK THE FUEL PRESSURE
WARNING: WHEN CHECKING THE FUEL SYSTEM REMEMBER THAT THE FUEL SYSTEM MAY STILL BE PRESSURIZED WHEN THE ENGINE IS SWITCHED OFF. ALWAYS FOLLOW THE INSTRUCTIONS RELATED TO FUEL SYSTEM PRESSURE RELIEF. ALL FUEL HANDLING SAFETY PRECAUTIONS MUST BE OBSERVED. FAILURE TO FOLLOW THESE INSTRUCTIONS MAY RESULT IN PERSONAL INJURY.
Note:For vehicle specific fuel pressure ranges, refer to the Fuel System Specification Chart in Pinpoint Test HC.
- Remove the jumper wire(s).
- Universal HO2S connector connected.
- Relieve the fuel pressure. Refer to the Workshop Manual Section 310-00, Fuel System for the Fuel System Pressure Release procedure.
- Mechanical fuel pressure gauge connected.
- Pressurize the fuel system. Refer to the Workshop Manual Section 310-00, Fuel System for the Fuel System Pressure Release procedure to pressurize the fuel system.
- Ignition ON, engine running.
- Allow the fuel pressure to stabilize.
- Ignition OFF.
- Ignition ON, engine running.
- Access the PCM and control the FP (MODE) PID.
- Run the fuel pump to obtain maximum fuel pressure.
Is the fuel pressure within range for the vehicle being diagnosed?
Yes
- GO to H12
.
No
- GO to Pinpoint Test HC See: Computers and Control Systems > Diagnostic Trouble Code Tests and Associated Procedures > HC: Fuel Delivery System - Introduction
.
H12 CHECK THE FUEL SYSTEM FOR PRESSURE STABILITY - FAST LEAKDOWN
Note:When the fuel pump is commanded off, the fuel pressure may substantially decrease and then stabilize.
Note

uring output state control, the fuel pump stays commanded on for approximately 5 seconds.
- Ignition OFF.
- Ignition ON, engine OFF.
- Access the PCM and control the FP (MODE) PID.
- Run the fuel pump to obtain maximum fuel pressure.
- Command the fuel pump off.
- Allow the fuel pressure to stabilize.
- Record the stabilized reading.
- Monitor the fuel pressure for 10 seconds.
Does the fuel pressure remain within 34 kPa (5 psi) of the recorded reading after 10 seconds?
Yes
- GO to H14
.
No
- GO to H13
.
H13 CHECK FOR AN EXTERNAL FUEL LEAK
- Inspect the fuel tank, lines, and filler pipe for a fuel leak.
Is a concern present?
Yes
- REPAIR as necessary.
- REFER to the fuel system WARNING information at the beginning of Pinpoint Test HC. GO to Pinpoint Test HC See: Computers and Control Systems > Diagnostic Trouble Code Tests and Associated Procedures > HC: Fuel Delivery System - Introduction
.
- RESET the keep alive memory (KAM). REFER to Section 2, Resetting The Keep Alive Memory (KAM) See: Computers and Control Systems > Diagnostic Trouble Code Tests and Associated Procedures > Resetting The Keep Alive Memory (KAM). REPEAT the self-test.
No
- For DTCs P219A or P219B, GO to H14
.
- For all others, GO to H21
.
H14 CHECK THE FUEL SYSTEM FOR PRESSURE STABILITY - SLOW LEAKDOWN
- Continue to monitor the fuel pressure for 1 minute.
Does the fuel pressure remain within 34 kPa (5 psi) of the recorded reading (MRFS) or greater than 275 kPa (40 psi) (ERFS) after 1 minute?
Yes
- For DTCs P219A or P219B, UNABLE to duplicate or identify the concern at this time.
- GO to Pinpoint Test Z See: Computers and Control Systems > Diagnostic Trouble Code Tests and Associated Procedures > Z: Intermittent - Introduction
.
- For all others, GO to H15
.
No
- GO to HC13 See: Computers and Control Systems > Diagnostic Trouble Code Tests and Associated Procedures > HC: Fuel Delivery System - Pinpoint Test
.
H15 CHECK THE SEPARATION LEVEL OF THE ETHANOL, WATER AND GASOLINE MIXTURE IN THE FUEL
Note:This step requires the use of a locally obtained 200 ml beaker and a 25 ml graduated cylinder.
Note:After approximately 3 minutes of standing, the ethanol and water mixes together and settles to the bottom of the 25 ml graduated cylinder. The gasoline rises to the top.
- Fill the 200 ml beaker with 5 ml of clean water.
- Use the pressure relief valve on the mechanical fuel gauge to drain 22 ml of fuel into an approved clean container.
- Pour 20 ml of fuel from the approved clean container into the 25 ml graduated cylinder.
- Add enough water from the 200 ml beaker to the 25 ml graduated cylinder to bring the total volume of liquid to 24 ml.
- Insert a stopper plug in the opening of the 25 ml graduated cylinder.
- Firmly hold the stopper in place and shake the 25 ml graduated cylinder to mix the water and fuel.
- Allow the liquid to stand and separate for approximately 3 minutes.
- Record the separation level from the 25 ml graduated cylinder where the ethanol and water mixture and gasoline meet.
Does the ethanol and water mixture and gasoline separate?
Yes
- GO to H16
.
No
- The ethanol and water mixture will separate from the gasoline. If the
fuel does not appear to separate, then the fuel is either 100% ethanol
or a mixture of ethanol and water. REPLACE the contaminated fuel.
- Clear the PCM DTCs. REPEAT the self-test.
H16 CALCULATE THE PERCENTAGE OF ETHANOL IN THE FUEL
Note:Use the illustration as an example for calculating the percentage of ethanol in the following steps. If the separation level is at 14 ml the calculation becomes; 14 minus 4, then multiply by 5 to equal 50. The percentage of ethanol in the fuel is 50%.
- Ignition OFF.
- Take the recorded separation level from the previous step and subtract the amount of water added.
- Multiply the new value by 5. This new value is the percentage of ethanol in the fuel.
Open In New Tab Zoom/Printimage
image
- Record the calculated percentage of ethanol in the fuel.
Is any ethanol present in the fuel?
Yes
- For flex fuel vehicles, GO to H17
.
- For all others, GO to H20
.
No
- For DTCs P0171, P0174, P2195 or P2197, GO to HC3 See: Computers and Control Systems > Diagnostic Trouble Code Tests and Associated Procedures > HC: Fuel Delivery System - Pinpoint Test
.
- For all others, GO to H21