On Board Diagnostics II PCED

1999 PCED On Board Diagnostics II

SECTION 5: Pinpoint Tests

HB: Natural Gas Fuel Delivery System

HB1 CHECK SYSTEM INTEGRITY

WARNING: BEFORE SERVICING OR REPLACING ANY COMPONENTS IN THE FUEL SYSTEM, REDUCE THE POSSIBILITY OF INJURY OR FIRE BY FOLLOWING DIRECTIONS IN FUEL SYSTEM WARNING, CAUTION AND NOTE AT THE BEGINNING OF THIS PINPOINT TEST.

Key on, engine off for 5 seconds.
Key off.
Visually inspect the complete fuel delivery system, including fuel lines, connections, fuel rail, pressure regulator and fuel injector areas for leaks (hissing noise), looseness, cracks, kinks, pinching, or abrasion caused by a collision or mishandling.
Visually inspect electrical harness and connectors for loose pins, corrosion, abrasion or other damage from collision or mishandling.
Verify vehicle has followed maintenance schedule.
Inspect fuel filter element for contamination and service as necessary.
Verify Inertia Fuel Shutoff (IFS) switch is set.
Verify vehicle battery is fully charged.
Verify electrical/fuse integrity.

Have any concerns been identified?

Yes	No
REPAIR as necessary. VERIFY a symptom no longer exists.	For symptom of poor fuel range: GO to NG fuel tank venting procedures located in the Powertrain/Fuel Systems Group in the Workshop Manual. For symptom of fuel smell: GO to HB16 . All other symptoms: GO to HB2 .

HB2 CHECK FUEL TANK PRESSURE

Install fuel tank venting tool (supplied in Tool Kit 134-00114) to vehicle fueling connector.
Open bypass on fill valve (refer to Powertrain/Fuel Systems Group in the Workshop Manual for this procedure).
Key on.
Record fuel tank pressure reading and fuel gauge reading.

Is the fuel pressure reading greater than 3,448 kPa (500 psi)?

Yes	No
KEY OFF. CLOSE bypass and REMOVE tool. GO to HB5 .	VERIFY fuel level. If OK, CHECK for power at tank solenoid valve. GO to HB3 .

HB3 CHECK VPWR VOLTAGE TO THE FUEL TANK SOLENOID SHUT-OFF VALVE

Key on.
Access Output Test Mode.
Select ALL ON.
Measure voltage between the VPWR and GND circuits at the fuel tank solenoid shut-off valve harness connector (refer to the Electrical and Vacuum Troubleshooting Manual for location).

Is the voltage reading greater than 10.5 volts?

Yes	No
GO to NG fuel tank venting procedures located in the Powertrain/Fuel Systems Group in the Workshop Manual for fuel tank solenoid shut-off valve diagnostics.	GO to HB4 .

HB4 CHECK FOR OPEN VPWR CIRCUIT BETWEEN FUEL TANK SOLENOID SHUT-OFF VALVE AND BATTERY GROUND

Key on.
Access Output Test Mode.
Select ALL ON.
Measure voltage between the VPWR circuit at the fuel tank solenoid shut-off valve harness connector and battery negative post.

Is the voltage reading greater than 10.5 volts?

Yes	No
REPAIR open VPWR circuit. VERIFY a symptom no longer exists.	REPAIR open GND circuit. VERIFY a symptom no longer exists.

HB5 CHECK FUEL PRESSURE

Observe WARNING, CAUTION AND NOTE.
Connect Fuel Pressure Tester to schrader valve.
Release fuel pressure in fuel injection supply manifold (fuel rail) and supply lines.
Key on, engine on (if possible, start engine).
Key off.
After two minutes, obtain pressure reading from pressure tester.

Is fuel pressure within 552 to 827 kPa (80 to 120 psi)?

Yes	No
For no starts: GO to HB6 .	REPLACE fuel pressure regulator. VERIFY a symptom no longer exists.

HB6 CHECK FUEL RAIL PRESSURE SENSOR ACCURACY

Observe WARNING, CAUTION and NOTE.
Fuel pressure tester connected with vent hose.
Connect scan tool.
Key on, engine off.
Note pressure of FRP sensor with scan tool.
Note pressure at schrader valve with fuel pressure tester.
Key off.
Slowly open the one quarter turn shut off valve on the fuel pressure tester and vent fuel pressure to 345-485 kPa (50-70 psi).
Remove the fuel pump relay.
Key on, engine off.
Note pressure of FRP sensor with scan tool.
Note pressure at schrader valve with pressure tester.
Key off.

Is the FRP sensor pressure constant and within 70 kPa (10 psi) of the pressure at the Schrader valve?

Yes	No
For no starts: GO to HB10 . For all others: Return to symptom chart.	GO to HB7 .

HB7 VERIFY FUEL RAIL SOLENOID SHUT-OFF VALVE OPENS

Observe WARNING, CAUTION and NOTE.
Fuel pressure tester connected with vent hose.
Key on, engine off.
Access Output Test Mode.
Select ALL ON and then START and STOP several times by toggling the START and STOP button on the scan tool and listening or feeling for a click at the fuel rail solenoid shut-off valve.
Key off.

Was a click of the solenoid valve felt or heard?

Yes	No
REPLACE fuel rail pressure sensor. RESTORE vehicle. VERIFY a symptom no longer exists.	GO to HB8 .

HB8 CHECK VPWR VOLTAGE TO THE FUEL RAIL SOLENOID SHUT-OFF VALVE

Key on, engine off.
Access Output Test Mode.
Select ALL ON, and START.
Measure the voltage between the VPWR and GND circuit at the fuel rail solenoid shut-off valve harness connector.

Note: This circuit remains on for only 8 seconds.

Is the voltage reading greater than 10.5 volts?

Yes	No
REPLACE fuel rail solenoid valve. RESTORE vehicle. VERIFY a symptom no longer exists.	GO to HB9 .

HB9 CHECK FOR OPEN VPWR CIRCUIT BETWEEN FUEL TANK SOLENOID SHUT-OFF VALVE AND BATTERY GROUND

Key on, engine off.
Access Output Test Mode.
Select ALL ON, and START.
Measure the voltage between the VPWR circuit at the fuel rail solenoid shut-off valve harness connector and battery negative post.

Note: This circuit remains on for only 8 seconds.

Is the voltage reading greater than 10.5 volts?

Yes	No
REPAIR open GND circuit. RESTORE vehicle. VERIFY a symptom no longer exists.	REPAIR open VPWR circuit. RESTORE vehicle. VERIFY a symptom no longer exists.

HB10 VERIFY FUEL RAIL SOLENOID SHUT-OFF VALVE SEALS

Observe WARNING, CAUTION and NOTE.
Fuel pressure tester connected with vent hose.
Vent fuel pressure in the fuel injection supply manifold (fuel rail) and supply lines.
Disconnect the fuel rail solenoid shut-off valve at the fuel injection supply manifold (fuel rail) harness connector.
Crank the engine for 3 seconds.
After two minutes, turn key on and access FRP PID and note pressure.

Is pressure at FRP sensor less than 70 kPa (10 psi)?

Yes	No
GO to HB11 .	REPLACE solenoid valve. RESTORE vehicle. VERIFY a symptom no longer exists.

HB11 VERIFY FUEL RAIL SOLENOID SHUT-OFF VALVE PARTIALLY OPENS

Observe WARNING, CAUTION and NOTE.
Key off.
Fuel pressure tester connected with vent hose.
Vent pressure in the fuel injection supply manifold (fuel rail) and supply lines.
Disconnect the fuel rail solenoid shut-off valve on the fuel injection supply manifold (fuel rail) at the harness connector.
Key on, engine off.
Key off.
Reconnect the fuel rail solenoid shut-off valve.
Key on, engine off.
Access the FRP PID.
Note the pressure on the pressure gauge.

Is the FRP sensor pressure within 70 kPa (10 psi) of the fuel pressure gauge after turning key on with the engine off?

Yes	No
KEY OFF. GO to HB12 .	REPLACE fuel rail solenoid shut-off valve. RESTORE vehicle. VERIFY a symptom no longer exists.

HB12 VERIFY FUEL RAIL SOLENOID SHUT-OFF VALVE FULLY OPENS

Observe WARNING, CAUTION and NOTE.
Fuel pressure tester connected with vent hose.
Vent pressure in the fuel injection supply manifold (fuel rail) and supply lines.
Disconnect the fuel rail solenoid shut-off valve on the fuel injection supply manifold (fuel rail) at the harness connector.
Key on, engine off.
Key off.
Reconnect the fuel rail solenoid shut-off valve.
Snap start the engine (Key on and immediately start the engine).
Immediately increase the engine speed to approximately 2500 rpm while monitoring the FRP PID.
Note the pressure on the pressure gauge.
Note the FRP pressure.

Is the FRP sensor pressure within 70 kPa (10 psi) of the pressure at the schrader valve?

Yes	No
KEY OFF. GO to HB13 .	REPLACE fuel rail solenoid shut-off valve. RESTORE vehicle. VERIFY a symptom no longer exists.

HB13 VERIFY FUEL PRESSURE WITH ENGINE ON

Observe WARNING, CAUTION and NOTE.
Key on, engine running.
Note FRP sensor pressure at idle with scan tool.
Increase engine speed to approximately 2500 rpm.
Note FRP sensor pressure at 2500 rpm with scan tool.

Is idle fuel pressure between 552 and 827 kPa (80 and 120 psi) and is pressure at 2500 rpm greater than 552 kPa (80 psi)?

Yes	No
KEY OFF. GO to HB14 .	VERIFY a blockage does not exist in fuel lines. REPLACE fuel pressure regulator. RESTORE vehicle. VERIFY a symptom no longer exists.

HB14 VERIFY REGULATOR THERMOSTAT

Observe WARNING, CAUTION and NOTE.
Key on, engine on.
Allow engine coolant to reach normal operating temperature.
CAREFULLY measure the temperature of fuel pressure regulator coolant bowl or coolant outlet with a thermometer or temperature probe.

Is the regulator temperature within 15° to 60° C (59° to 140°F)?

Yes	No
KEY OFF. GO to HB15 .	If fuel regulator coolant bowl is less than 15°C (59°F): KEY OFF. CHECK coolant lines and coolant system for proper operation. If OK, REPLACE fuel pressure regulator. If fuel regulator coolant bowl is greater than 60° C (140°F): KEY OFF. REPLACE pressure regulator. RESTORE vehicle. VERIFY a symptom no longer exists.

HB15 VERIFY FUEL INJECTOR FLOW

Note: SBDS® may be used for Injector Flow Testing when available.

Observe WARNING, CAUTION and NOTE.
Key off.
Key on, engine off.
Note initial FRP sensor pressure using the scan tool.
Electronic fuel injector tester installed to suspect fuel injector.
Select pulse width of 200 m sec.
Activate the fuel injector tester.
Note final FRP sensor pressure using scan tool.
Subtract final pressure from initial pressure to find pressure drop.
Repeat above test procedures for all remaining fuel injectors.

Is the pressure drop within 241 to 345 kPa (35 to 50 psi) and all fuel injectors within 20 kPa (3 psi) of each other?

Yes	No
RETURN to Section 3 , Symptom Charts, for additional symptom diagnostics.	KEY OFF. REPLACE fuel injector(s) that does not meet pressure specification. RESTORE vehicle. VERIFY a symptom no longer exists.

HB16 FUEL LEAK CHECK

Possible causes:

Loose fitting connectors.
Damaged or worn seals or fittings.
Damaged fuel lines or fuel system components.

Note: After the vehicle has soaked for several hours (has not run), a slight natural gas smell may emanate from within the intake manifold and intake air system. This is normal, as the fuel injectors leak down from the fuel rail to the intake manifold over several hours.

Key off.
Install fuel rail pressure gauge.
Key on, engine off (verify pressure is greater than 586 kPa (85 psi)). If the fuel system does have a fuel leak, it will be necessary to repeat this step to maintain pressure.
Check for leaks with the natural gas sniffer provided in Rotunda tool kit 134-00114 or a soapy water solution such as Snoop. Cover the complete joint with this solution. Examine the components or joints for 60 seconds for signs of bubbles.

Are any leaks indicated?

Yes	No
VERIFY proper torque on suspect fuel system components. RECHECK for leaks. If leaks still exist, REPAIR or REPLACE as necessary. RESTORE vehicle.	No leaks detected. No further diagnostics are required. RESTORE vehicle.

HB17 DTC P1180 AND P1181: CHECK FUEL PRESSURE

Inspect the fuel lines, regulator and fuel filter for restrictions or leaks.

Are there any concerns?

Yes	No
REPAIR as necessary. COMPLETE PCM Reset to clear DTC (REFER to Section 2 , Powertrain Control Module (PCM) Reset).	GO to HB18 .

HB18 CHECK FUEL TANK PRESSURE

Key on, engine running and vehicle in park.
Scan tool connected.
Access and monitor the TANKPR PID from the NGVM menu and record the value.
Access and monitor the FRP PID from the PCM menu and record the value.
Locate the approximate TANKPR value on the chart below, from this value determine the PCM inferred pressure.

Is the PCM inferred pressure ±22 psi of the fuel rail pressure (FRP) recorded?

Fuel Tank Pressure in kPa	PCM Inferred Pressure (psi)	Fuel Tank Pressure in kPa	PCM Inferred Pressure (psi)
30000	94	13000	102.25
28000	95.5	12000	102.5
26000	96	11000	103
24000	96	10000	103.38
23000	96.31	9000	104.5
22000	97.25	8000	105
21000	97.5	7000	105.56
20000	98.5	6000	106
19000	99	5000	106.5
18000	99.31	4000	106.88
17000	99.75	3000	108.44
16000	100.75	2000	109
14000	101.75	0	0

Yes	No
ADDRESS other Continuous Memory DTCs if present. If no other DTCs are present, COMPLETE PCM Reset to clear DTC (REFER to Section 2 , Powertrain Control Module (PCM) Reset).	For DTC P1180: GO to HB19 . For DTC P1181: REPLACE fuel pressure regulator. COMPLETE PCM Reset to clear DTC (REFER to Section 2 , Powertrain Control Module (PCM) Reset).

HB19 CHECK FUEL FILTER FOR WATER OR OTHER CONTAMINATION

Disassemble fuel filter and check for water and other contamination.

Is there any contamination present?

Yes	No
CLEAN contaminants from filter housing. REPLACE filter element.	GO to HB20 .

HB20 CHECK FUEL LINE FOR RESTRICTION

Visually inspect all fuel lines for damage which may cause the fuel to be restricted or leaking.

Are there any restrictions?

Yes	No
REPAIR fuel line(s) as required. COMPLETE PCM Reset to clear DTC (REFER to Section 2 , Powertrain Control Module (PCM) Reset).	REPLACE fuel pressure regulator. COMPLETE PCM Reset to clear DTC (REFER to Section 2 , Powertrain Control Module (PCM) Reset).