On Board Diagnostics II PCED

1999 PCED On Board Diagnostics II

SECTION 5: Pinpoint Tests

DC: Mass Air Flow (MAF) Sensor

DC1 DTC P1101: CHECK FOR MAF SENSOR CONTINUOUS MEMORY DTCs

Drive vehicle for 6 to 10 minutes.
Rerun KOER, KOEO Self-Test and retrieve Continuous Memory DTCs.

Is a Continuous Memory DTC present with the KOER DTC P1101?

Yes	No
For Continuous Memory DTC P0102: GO to DC2 . For Continuous Memory DTC P0103: GO to DC20 All other Continuous Memory DTCs: GO to Section 4 , Powertrain Diagnostic Trouble Code (DTC) Charts.	KEY OFF. GO to DC3 .

DC2 DTC P0102: CHECK MAF SENSOR SIGNAL LOW INPUT TO PCM

Check for broken/loose air outlet tube clamps (throttle body and air cleaner assembly ends), cracks/holes in air outlet tube, worn gaskets between MAF sensor and air cleaner assembly. Repair as necessary.
Start engine and bring to idle.
If a KOER DTC P0505 is present, go to Section 4 , Powertrain Diagnostic Trouble Code (DTC) Charts. For A/T vehicles, if the engine stalls and cannot maintain an idle, GO to DC7 .
Run engine up 1500 rpm for 5 seconds, then bring it back to idle.
Access MAF PID (MAF V PID).

Is MAF PID (MAF V PID) less than 0.23 volt (refer to Voltage to Mass Air Flow Conversion Table at beginning of this pinpoint test)?

Yes	No
KEY OFF. GO to DC4 .	KEY OFF. GO to DC3 .

DC3 DTC P1101: CHECK FOR MAF SENSOR SIGNAL OUT OF SELF-TEST RANGE

Note: DTC P1101 can be generated by a low charged vehicle battery or the garage exhaust ventilation system. Repair battery as necessary. Then remove ventilation system and properly vent to outside atmosphere. Rerun KOEO Self-Test.

Verify MAF sensor is connected. If not, repair as necessary.
Key on, engine running.
Access MAF PID (MAF V PID).

Is MAF PID (MAF V PID) between 0.46-2.44 volts (refer to Voltage to Mass Air Flow Conversion Table at beginning of this pinpoint test)?

Yes	No
Unable to identify fault at this time. GO to Z1 .	KEY OFF. GO to DC4 .

DC4 CHECK VPWR VOLTAGE TO MAF SENSOR

Note: Refer to the PCM connector pin numbers in the beginning of this pinpoint test.

Disconnect MAF sensor.
Key on, engine off.
Measure voltage between VPWR circuit at the MAF sensor harness connector and battery negative post.

Is voltage greater than 10.5 volts?

Yes	No
GO to DC5 .	REPAIR open circuit. RESET Keep Alive Random Access Memory (RAM) (REFER to Section 2 , Powertrain Control Module (PCM) Reset).

DC5 CHECK PWR GND CIRCUIT BETWEEN MAF SENSOR AND POWER RELAY

Measure voltage between PWR GND circuit at the MAF sensor harness connector and battery positive post.

Is voltage greater than 10.0 volts?

Yes	No
KEY OFF. GO to DC6 .	REPAIR open circuit. RESET Keep Alive Random Access Memory (RAM) (REFER to Section 2 , Powertrain Control Module (PCM) Reset).

DC6 CHECK VPWR CIRCUIT FOR OPEN IN HARNESS

Note: Refer to the PCM connector pin numbers in the beginning of this pinpoint test.

Disconnect PCM.
Measure resistance of VPWR circuit between PCM harness connector pin (or on LS6/LS8 the VPWR fuse to the power relay) and MAF sensor harness connector.

Is resistance less than 5.0 ohms?

Yes	No
GO to DC7 .	REPAIR open circuit. RESET Keep Alive Random Access Memory (RAM) (REFER to Section 2 , Powertrain Control Module (PCM) Reset).

DC7 CHECK MAF CIRCUIT SHORT TO PWR GND OR MAF RTN IN THE HARNESS

PCM disconnected.
Disconnect scan tool from DLC.
Measure resistance between MAF and PWR GND circuits at the MAF sensor harness connector.
Measure resistance between MAF and MAF RTN circuits at the MAF sensor harness connector.

Is each resistance greater than 10,000 ohms?

Yes	No
GO to DC8 .	REPAIR short circuit. RESET Keep Alive Random Access Memory (RAM) (REFER to Section 2 , Powertrain Control Module (PCM) Reset).

DC8 CHECK MAF RTN CIRCUIT SHORT TO PWR GND IN THE HARNESS

Measure resistance between MAF RTN and PWR GND circuits at the MAF sensor harness connector.

Is the resistance greater than 10,000 ohms?

Yes	No
RECONNECT scan tool to DLC. GO to DC9 .	REPAIR short circuit. RESET Keep Alive Random Access Memory (RAM) (REFER to Section 2 , Powertrain Control Module (PCM) Reset).

DC9 CHECK MAF CIRCUIT VOLTAGE CYCLING INTEGRITY

Reconnect PCM.
Key on, engine off.
Access MAF PID (MAF V PID).
Record the MAF PID (MAF V PID) reading.
Jumper MAF RTN and PWR GND circuits at the MAF sensor harness connector.
Jumper MAF and VPWR circuits at the MAF sensor harness connector.

Does the MAF PID (MAF V PID) change from less than 0.23 volt (closer to zero volts) to greater than 4.50 volts (refer to Voltage to Mass Air Flow Conversion Table at beginning of this pinpoint test)?

Yes	No
REPLACE MAF sensor. RESET Keep Alive Random Access Memory (RAM)(REFER to Section 2 , Powertrain Control Module (PCM) Reset).	For DTC P1101 without P0102 present: KEY OFF. GO to DC11 . For DTC P0102: KEY OFF. GO to DC10 .

DC10 CHECK MAF CIRCUIT FOR OPEN IN HARNESS

Note: Refer to the PCM connector pin numbers in the beginning of this pinpoint test.

Disconnect PCM.
Measure resistance of MAF circuit between PCM harness connector pin and MAF sensor harness connector.

Is resistance less than 5.0 ohms?

Yes	No
GO to DC11 .	REPAIR open circuit. RESET Keep Alive Random Access Memory (RAM) (REFER to Section 2 , Powertrain Control Module (PCM) Reset).

DC11 CHECK PWR GND CIRCUIT FOR OPEN IN HARNESS

PCM disconnected.
Disconnect scan tool from DLC.
Measure resistance of PWR GND circuit between MAF sensor harness connector and battery negative post.

Is resistance less than 10 ohms?

Yes	No
RECONNECT scan tool. GO to DC12 .	REPAIR open circuit. RESET Keep Alive Random Access Memory (RAM) (REFER to Section 2 , Powertrain Control Module (PCM) Reset).

DC12 CHECK MAF RTN FOR OPEN IN HARNESS

Note: Refer to the PCM connector pin numbers in the beginning of this pinpoint test.

Measure resistance of MAF RTN circuit between PCM harness connector pin and MAF sensor harness connector.

Is resistance less than 5.0 ohms?

Yes	No
REPLACE PCM (refer to Section 2 , Flash EEPROM).	REPAIR open circuit. RESET Keep Alive Random Access Memory (RAM) (REFER to Section 2 , Powertrain Control Module (PCM) Reset).

DC16 DTC P1100: CHECK MAF CIRCUIT FOR INTERMITTENT VOLTAGE TO PCM

Start engine and bring it to idle.
If a stable idle is not at least 700 rpm, GO to Section 3 , Symptom Charts.
Run throttle up to 1500 rpm for 5 seconds, and bring back to idle.
Access MAF PID (MAF V PID) while completing the following:

Lightly tap on MAF sensor and wiggle harness connector to simulate road shock.

Is MAF PID (MAF V PID) changing below the minimum 0.23 volt or above a maximum 4.60 volts (refer to Voltage to Mass Air Flow Conversion Table at beginning of this pinpoint test)?

Yes	No
INSPECT MAF sensor connector. If OK, REPLACE the MAF sensor. RESET Keep Alive Random Access Memory (RAM) (REFER to Section 2 , Powertrain Control Module (PCM) Reset).	GO to DC17 .

DC17 CHECK FOR MAF SENSOR CIRCUIT FOR INTERMITTENT OPENS OR SHORTS

Again access the MAF PID (MAF V PID).
Key on, engine off.
Complete the following:

Grasp the MAF sensor harness and MAF sensor harness connector.
Shake and bend a small section of the harness all the way to the dash panel.
Wiggle, shake and bend the harness from the dash panel to the PCM.

Is the MAF PID (MAF V PID) reading changing below the minimum 0.23 volt or above the maximum 4.60 volts (refer to Voltage to Mass Air Flow Conversion Table at the beginning of this pinpoint test)?

Yes	No
REPAIR as necessary. RESET Keep Alive Random Access Memory (RAM)(REFER to Section 2 , Powertrain Control Module (PCM) Reset).	Unable to duplicate or identify fault at this time. GO to Pinpoint Test Step Z1 .

DC20 DTC P0103: CHECK MAF SENSOR SIGNAL HIGH INPUT TO PCM

Note: DTC P0103 can be generated by foreign material blocking the MAF sensor screen causing an air flow restriction. If contaminants are found on the screen, check air cleaner element installation in air cleaner housing and proper sealing of air cleaner and air tubes before proceeding. Rerun Quick Test after service.

Start engine and bring to idle.
If a KOER DTC P0505 is present, GO to Section 4 , Powertrain Diagnostic Trouble Code (DTC) Charts. For 2.5L A/T Ranger that stalls and cannot maintain an idle, REPLACE PCM (refer to Section 2 , Flash EEPROM).
Run throttle up to 1500 rpm for 5 seconds, and bring it back to idle.

Note: MAF PID (MAF V PID) is greater than 4.60 volts (refer to Voltage To Mass Air Flow Conversion Table at the beginning of this pinpoint test).

Access MAF PID (MAF V PID).
Key off.
Disconnect MAF sensor.
Jumper PWR GND and MAF RTN circuits at the MAF sensor harness connector.
Key on, engine running.
Again access MAF PID (MAF V PID).

Did MAF PID (MAF V PID) drop from the previous reading to below 0.23 volt (refer to Voltage To Mass Air Flow Conversion Table at the beginning of this pinpoint test)?

Yes	No
REMOVE jumper. REPLACE MAF sensor. RESET Keep Alive Random Access Memory (RAM) (REFER to Section 2 , Powertrain Control Module (PCM) Reset).	KEY OFF. REMOVE jumper. GO to DC21 .

DC21 CHECK MAF CIRCUIT FOR SHORT TO VPWR IN HARNESS

Note: Refer to the PCM connector pin numbers in the beginning of this pinpoint test.

Disconnect PCM.
Key on, engine off.
Measure voltage between MAF and PWR GND circuits at the PCM harness connector.

Is voltage less than 1.0 volt?

Yes	No
KEY OFF. GO to DC22 .	REPAIR short circuit.

DC22 CHECK MAF CIRCUIT FOR SHORT TO VREF IN HARNESS

Measure resistance between MAF and VREF circuits at the PCM harness connector. (For LS6/LS8 measure to both VREF pins.)

Is resistance greater than 10,000 ohms?

Yes	No
If an idle concern is not present: REPLACE PCM (refer to Section 2 , Flash EEPROM). If a fault was not detected and an idle concern is still present: Disregard DTC P0102 at this time. RETURN to Section 4 , Diagnostic Subroutines.	REPAIR short circuit. RESET Keep Alive Random Access Memory (RAM)(REFER to Section 2 , Powertrain Control Module (PCM) Reset).

DC25 DTC P0171, P0172, P0174, P0175 OR LEAN DRIVEABILITY CONCERNS: CHECK CONDITIONS RELATED TO MAF SENSOR

Note: Most weather service reports are a local barometric pressure that has been corrected to sea level. However, the BARO PID reports the actual barometric pressure for the altitude the vehicle is being diagnosed in. Local weather conditions (high or low pressure areas) will change the local barometric pressure by several inches of Mercury (± 3 Hz. (± 1 in. -Hg.))

Verify the MAF sensor is connected.
If not, repair as necessary.
Key on, engine running.
Access the BARO, LONGFT1, LONGFT2 and MAF V PIDs with a Scan Tool on a fully warmed up engine.
Check that the BARO PID is approximately the same as the barometric pressure reading for the location, day and altitude the vehicle is being diagnosed at.

BARO PID values in Keep Alive Memory require updating at high throttle openings. If the vehicle is driven down from higher altitudes for diagnosing, complete three or four heavy accelerations at greater than half-throttle to allow BARO PID to update.
BARO PID must be within ± 6 Hz. (± 2 in. -Hg.) of the altitude value in Barometric Pressure Reference Chart (at the beginning of this pinpoint test).
Make BARO PID comparisons to Barometric Pressure Reference Chart, daily airport barometric pressure reports or the present Service Bay Diagnostic System (SBDS) built-in MAP sensor test reading.

Check that the LONGFT1 and LONGFT2 PIDS for all injector banks at idle is not more negative than -12 %.
Check that the MAF V PID at idle and neutral is not greater than 30 % of the normal MAF V listed in Section 6 , Reference Values (or not greater than 1.1 volts.)

Are two of the above three checks ok?

Yes	No
For DTC P0171, P0172, P0174 or P0175: GO to Pinpoint Step H42 (or HA42 for natural gas vehicles only). For driveability symptoms without DTCs: RETURN to Section 3 , Symptom Charts for further diagnosis.	KEY OFF. Go to DC26 .

DC26 CHECK TO ISOLATE MAF SENSOR FROM LEAN DRIVEABILITY OCCURRENCE

Note: Due to increasingly stringent emission/OBD II requirements, a fuel system DTC on some vehicles will be generated without a noticeable driveability concern with or without the MAF sensor disconnected. Under these conditions, if the BARO, LONGFT1, LONGFT2 and MAF V PID indicates a MAF sensor fault, replace the MAF sensor.

Key off.
Disconnect MAF sensor.
Key on, engine running.
Drive the vehicle from 10 to 20 minutes.

Is the lean driveability symptom (lack of power, spark knock/detonation, buck/jerk or hesitation/surge on acceleration) gone?

Yes	No
REPLACE MAF sensor. RESET Keep Alive Random Access Memory (RAM) (REFER to Section 2 , Powertrain Control Module (PCM) Reset). VERIFY a symptom no longer exists.	For DTC P0171, P0172, P0174 or P0175: GO to Pinpoint Test Step H42 (or HA42 for natural gas vehicles only). For lean driveability symptoms listed without DTCs: RETURN to Section 3 , Symptom Charts for further diagnosis.