Code No. 25 Barometric Pressure Sensor System

OPERATION

A power voltage of 5 V is applied to the barometric pressure sensor power terminal (terminal No. 1) of the air flow sensor connector from the engine-A/T-ECU (terminal No. 46) and earthed to the engine-A/T-ECU (terminal No. 16) from the air flow sensor (terminal No. 5).

The sensor signal is inputted to the engine-A/T-ECU (terminal No. 55) from the barometric pressure sensor output terminal (terminal No. 2) of the air flow sensor connector.

FUNCTION

The barometric pressure sensor converts the barometric pressure into a voltage signal and inputs the signal to the engine-A/T-ECU.

In response to the signal, the engine-A/T-ECU corrects the fuel injection amount, etc.

TROUBLE JUDGMENT

Check Conditions

60 seconds later after the ignition switch has been in "ON" position or the engine has started up.

Battery voltage of 8 V or more.

Judgment Criteria

A sensor output voltage of 4.5 V or more (atmospheric pressure above 114 kPa or equivalent) for 4 seconds,

A sensor output voltage of 0.2 V or less (atmospheric pressure below 5 kPa or equivalent) for 4 seconds.

PROBABLE CAUSE

Failed barometric pressure sensor

Open/short circuit in atmospheric pressure sensor circuit or loose connector contact

Failed engine-A/T-ECU

DIAGNOSIS PROCEDURE

STEP 1. MUT-II/III data list

Refer to Data list reference table .

Item 25: Barometric pressure sensor

Q: Is the check result normal?

YES: Intermittent malfunction (Refer to GROUP 00 - How to Use Troubleshooting/Inspection Service Points

).
NO: Go to Step 2

STEP 2. Connector check: B-08 air flow sensor connector

Q: Is the check result normal?

YES: Go to Step 3

.
NO: Repair.

STEP 3. Perform voltage measurement at B-08 air flow sensor connector.

Disconnect connector, and measure at harness side.

Ignition switch: ON

Voltage between terminal No. 1 and earth.

OK: 4.9 - 5.1 V

Q: Is the check result normal?

YES: Go to Step 9

.
NO: Go to Step 4

STEP 4. Perform voltage measurement at C-111 engine-A/T-ECU connector.

Measure engine-A/T-ECU terminal voltage.

Ignition switch: ON

Voltage between terminal No. 46 and earth.

OK: 4.9 - 5.1 V

Q: Is the check result normal?

YES: Go to Step 5

.
NO: Go to Step 6

STEP 5. Connector check: C-111 engine-A/T-ECU connector

Q: Is the check result normal?

YES:

Check and repair harness between B-08 (terminal No. 1) air flow sensor connector and C-111 (terminal No. 46) engine-A/T-ECU connector.

Check power supply line for open circuit.

NO: Repair.

STEP 6. Connector check: C-111 engine-A/T-ECU connector

Q: Is the check result normal?

YES: Go to Step 7

.
NO: Repair.

STEP 7. Check harness between B-08 (terminal No. 1) air flow sensor connector and C-111 (terminal No. 46) engine-A/T-ECU connector.

Check power supply line for short circuit.

Q: Is the check result normal?

YES: Go to Step 8

.
NO: Repair.

STEP 8. MUT-II/III data list

Refer to Data list reference table .

Item No. 25: Barometric pressure sensor

Q: Is the check result normal?

YES: Intermittent malfunction (Refer to GROUP 00 - How to Use Troubleshooting/Inspection Service Points

).
NO: Replace engine-A/T-ECU.

STEP 9. Perform voltage measurement at B-08 air flow sensor connector.

Disconnect connector, and measure at harness side.

Voltage between terminal No. 5 and earth.

OK: 2 Ω or less

Q: Is the check result normal?

YES: Go to Step 12

.
NO: Go to Step 10

STEP 10. Connector check: C-112 engine-A/T-ECU connector

Q: Is the check result normal?

YES: Go to Step 11

.
NO: Repair.

STEP 11. Check harness between B-08 (terminal No. 5) air flow sensor connector and C-112 (terminal No. 16) engine-A/T-ECU connector.

NOTE: Before checking harness, check intermediate connector C-16, and repair if necessary.

Check earthing line for open circuit and damage.

Q: Is the check result normal?

YES: Go to Step 8

.
NO: Repair.

STEP 12. Perform voltage measurement at B-08 air flow sensor connector.

Use special tool test harness (MB991709) to connect only terminal No. 1, No. 2 and No. 5, and then measure at pick-up harness.

Ignition switch: ON

Voltage between terminal No. 1 and earth.

OK: 4.9 - 5.1 V

Q: Is the check result normal?

YES: Go to Step 14

.
NO: Go to Step 13

STEP 13. Connector check: C-111 engine-A/T-ECU connector

Q: Is the check result normal?

YES:

Check and repair harness between B-08 (terminal No. 1) air flow sensor connector and C-111 (terminal No. 46) engine-A/T-ECU connector.

Check power supply line for damage.

NO: Repair.

STEP 14. Perform voltage measurement at B-08 air flow sensor connector.

Use special tool test harness (MB991709) to connect only terminal No. 1, No. 2 and No. 5, and then measure at pick-up harness.

Ignition switch: ON

Voltage between terminal No. 5 and earth.

OK: 0.5 V or less

Q: Is the check result normal?

YES: Go to Step 16

.
NO: Go to Step 15

STEP 15. Connector check: C-112 engine-A/T-ECU connector

Q: Is the check result normal?

YES:

Check intermediate connector C-16, and repair if necessary. If intermediate connector is normal, check and repair harness between B-08 (terminal No. 5) air flow sensor connector and C-112 (terminal No. 16) engine-A/T-ECU connector.

Check earthing line for damage.

NO: Repair.

STEP 16. Perform voltage measurement at B-08 air flow sensor connector.

Use special tool test harness (MB991709) to connect only terminal No. 1, No. 2 and No. 5, and then measure at pick-up harness.

Ignition switch: ON

Voltage between terminal No. 2 and earth.

OK:

Altitude 0 m: 3.8 - 4.2 V

Altitude 600 m: 3.5 - 3.9 V

Altitude 1,200 m: 3.3 - 3.7 V

Altitude 1,800 m: 3.0 - 3.4 V

Q: Is the check result normal?

YES: Go to Step 19

.
NO: Go to Step 17

STEP 17. Connector check: C-111 engine-A/T-ECU connector

Q: Is the check result normal?

YES: Go to Step 18

.
NO: Repair.

STEP 18. Check harness between B-08 (terminal No. 2) air flow sensor connector and C-111 (terminal No. 55) engine-A/T-ECU connector.

Check output line for short circuit and damage.

Q: Is the check result normal?

YES: Replace air flow sensor.
NO: Repair.

STEP 19. Perform voltage measurement at C-111 engine-A/T-ECU connector.

Measure engine-A/T-ECU terminal voltage.

Ignition switch: ON

Voltage between terminal No. 55 and earth.

OK:

Altitude 0 m: 3.8 - 4.2 V

Altitude 600 m: 3.5 - 3.9 V

Altitude 1,200 m: 3.3 - 3.7 V

Altitude 1,800 m: 3.0 - 3.4 V

Q: Is the check result normal?

YES: Go to Step 21

.
NO: Go to Step 20

STEP 20. Connector check: C-111 engine-A/T-ECU connector

Q: Is the check result normal?

YES:

Check and repair harness between B-08 (terminal No. 2) air flow sensor connector and C-111 (terminal No. 55) engine-A/T-ECU connector.

Check output line for open circuit and damage.

NO: Repair.

STEP 21. Connector check: C-111 engine-A/T-ECU connector

Q: Is the check result normal?

YES: Go to Step 8

.
NO: Repair.


Code No. 25 Barometric Pressure Sensor System

OPERATION A power voltage of 5 V is applied to the barometric pressure sensor power terminal (terminal No. 1) of the air flow sensor connector from the engine-A/T-ECU (terminal No. 46) and earthed to the engine-A/T-ECU (terminal No. 16) from the air flow sensor (terminal No. 5). The sensor signal is inputted to the engine-A/T-ECU (terminal No. 55) from the barometric pressure sensor output terminal (terminal No. 2) of the air flow sensor connector.
FUNCTION The barometric pressure sensor converts the barometric pressure into a voltage signal and inputs the signal to the engine-A/T-ECU. In response to the signal, the engine-A/T-ECU corrects the fuel injection amount, etc.
TROUBLE JUDGMENT Check Conditions 60 seconds later after the ignition switch has been in "ON" position or the engine has started up. Battery voltage of 8 V or more. Judgment Criteria A sensor output voltage of 4.5 V or more (atmospheric pressure above 114 kPa or equivalent) for 4 seconds, or A sensor output voltage of 0.2 V or less (atmospheric pressure below 5 kPa or equivalent) for 4 seconds.
PROBABLE CAUSE Failed barometric pressure sensor Open/short circuit in atmospheric pressure sensor circuit or loose connector contact Failed engine-A/T-ECU
	DIAGNOSIS PROCEDURE

	STEP 1. MUT-II/III data list Refer to Data list reference table . Item 25: Barometric pressure sensor Q: Is the check result normal? YES: Intermittent malfunction (Refer to GROUP 00 - How to Use Troubleshooting/Inspection Service Points). NO: Go to Step 2 .
	STEP 2. Connector check: B-08 air flow sensor connector
	Q: Is the check result normal? YES: Go to Step 3 . NO: Repair.
	STEP 3. Perform voltage measurement at B-08 air flow sensor connector.
	Disconnect connector, and measure at harness side. Ignition switch: ON Voltage between terminal No. 1 and earth. OK: 4.9 - 5.1 V Q: Is the check result normal? YES: Go to Step 9 . NO: Go to Step 4 .
	STEP 4. Perform voltage measurement at C-111 engine-A/T-ECU connector.
	Measure engine-A/T-ECU terminal voltage. Ignition switch: ON Voltage between terminal No. 46 and earth. OK: 4.9 - 5.1 V Q: Is the check result normal? YES: Go to Step 5 . NO: Go to Step 6 .
	STEP 5. Connector check: C-111 engine-A/T-ECU connector
	Q: Is the check result normal? YES: Check and repair harness between B-08 (terminal No. 1) air flow sensor connector and C-111 (terminal No. 46) engine-A/T-ECU connector. Check power supply line for open circuit. NO: Repair.
	STEP 6. Connector check: C-111 engine-A/T-ECU connector
	Q: Is the check result normal? YES: Go to Step 7 . NO: Repair.
	STEP 7. Check harness between B-08 (terminal No. 1) air flow sensor connector and C-111 (terminal No. 46) engine-A/T-ECU connector.
	Check power supply line for short circuit. Q: Is the check result normal? YES: Go to Step 8 . NO: Repair.
	STEP 8. MUT-II/III data list Refer to Data list reference table . Item No. 25: Barometric pressure sensor Q: Is the check result normal? YES: Intermittent malfunction (Refer to GROUP 00 - How to Use Troubleshooting/Inspection Service Points ). NO: Replace engine-A/T-ECU.
	STEP 9. Perform voltage measurement at B-08 air flow sensor connector.
	Disconnect connector, and measure at harness side. Voltage between terminal No. 5 and earth. OK: 2 Ω or less Q: Is the check result normal? YES: Go to Step 12 . NO: Go to Step 10 .
	STEP 10. Connector check: C-112 engine-A/T-ECU connector
	Q: Is the check result normal? YES: Go to Step 11 . NO: Repair.
	STEP 11. Check harness between B-08 (terminal No. 5) air flow sensor connector and C-112 (terminal No. 16) engine-A/T-ECU connector.
	NOTE: Before checking harness, check intermediate connector C-16, and repair if necessary. Check earthing line for open circuit and damage. Q: Is the check result normal? YES: Go to Step 8 . NO: Repair.
	STEP 12. Perform voltage measurement at B-08 air flow sensor connector.
	Use special tool test harness (MB991709) to connect only terminal No. 1, No. 2 and No. 5, and then measure at pick-up harness. Ignition switch: ON Voltage between terminal No. 1 and earth. OK: 4.9 - 5.1 V Q: Is the check result normal? YES: Go to Step 14 . NO: Go to Step 13 .
	STEP 13. Connector check: C-111 engine-A/T-ECU connector
	Q: Is the check result normal? YES: Check and repair harness between B-08 (terminal No. 1) air flow sensor connector and C-111 (terminal No. 46) engine-A/T-ECU connector. Check power supply line for damage. NO: Repair.
	STEP 14. Perform voltage measurement at B-08 air flow sensor connector.
	Use special tool test harness (MB991709) to connect only terminal No. 1, No. 2 and No. 5, and then measure at pick-up harness. Ignition switch: ON Voltage between terminal No. 5 and earth. OK: 0.5 V or less Q: Is the check result normal? YES: Go to Step 16 . NO: Go to Step 15 .
	STEP 15. Connector check: C-112 engine-A/T-ECU connector
	Q: Is the check result normal? YES: Check intermediate connector C-16, and repair if necessary. If intermediate connector is normal, check and repair harness between B-08 (terminal No. 5) air flow sensor connector and C-112 (terminal No. 16) engine-A/T-ECU connector. Check earthing line for damage. NO: Repair.
	STEP 16. Perform voltage measurement at B-08 air flow sensor connector.
	Use special tool test harness (MB991709) to connect only terminal No. 1, No. 2 and No. 5, and then measure at pick-up harness. Ignition switch: ON Voltage between terminal No. 2 and earth. OK: Altitude 0 m: 3.8 - 4.2 V Altitude 600 m: 3.5 - 3.9 V Altitude 1,200 m: 3.3 - 3.7 V Altitude 1,800 m: 3.0 - 3.4 V Q: Is the check result normal? YES: Go to Step 19 . NO: Go to Step 17 .
	STEP 17. Connector check: C-111 engine-A/T-ECU connector
	Q: Is the check result normal? YES: Go to Step 18 . NO: Repair.
	STEP 18. Check harness between B-08 (terminal No. 2) air flow sensor connector and C-111 (terminal No. 55) engine-A/T-ECU connector.
	Check output line for short circuit and damage. Q: Is the check result normal? YES: Replace air flow sensor. NO: Repair.
	STEP 19. Perform voltage measurement at C-111 engine-A/T-ECU connector.
	Measure engine-A/T-ECU terminal voltage. Ignition switch: ON Voltage between terminal No. 55 and earth. OK: Altitude 0 m: 3.8 - 4.2 V Altitude 600 m: 3.5 - 3.9 V Altitude 1,200 m: 3.3 - 3.7 V Altitude 1,800 m: 3.0 - 3.4 V Q: Is the check result normal? YES: Go to Step 21 . NO: Go to Step 20 .
	STEP 20. Connector check: C-111 engine-A/T-ECU connector
	Q: Is the check result normal? YES: Check and repair harness between B-08 (terminal No. 2) air flow sensor connector and C-111 (terminal No. 55) engine-A/T-ECU connector. Check output line for open circuit and damage. NO: Repair.
	STEP 21. Connector check: C-111 engine-A/T-ECU connector
	Q: Is the check result normal? YES: Go to Step 8 . NO: Repair.