Inspection Procedure 4

Inspection Procedure 4: In Spite of Abnormally Low Tire Pressure at a Road Wheel, the TPMS Warning Light does not Illuminate.

SYSTEM OPERATION

The TPMS warning light will illuminate when the ignition switch is turned to the "ON"
position if tire pressure of any road wheel is low.

TECHNICAL DESCRIPTION (COMMENT)

- The TPMS may not detect a failure if the TPMS transmitter does not send timely information or there is any interference with the antenna.
- The tire pressure sensor or driving G sensor inside the TPMS transmitter may be inaccurate or defective. In this case, the TPMS may not detect a failure.

TROUBLESHOOTING HINTS (THE MOST LIKELY CAUSES FOR THIS CASE:)

- The TPMS transmitter does not send timely information or there is any interference with the antenna.
- Damaged harness wire or connector
- Malfunction of the combination meter
- Malfunction of the TPMS transmitter
- Malfunction of the TPMS receiver

DIAGNOSIS

Required Special Tools:

- MB991958: Scan Tool (M.U.T.-III Sub Assembly)
- MB991824: Vehicle Communication Interface (V.C.I.)
- MB991827: M.U.T.-III USB Cable
- MB991910: M.U.T.-III Main Harness A

STEP 1. Check the TPMS warning light.

Check whether the TPMS warning light illuminates for three seconds after the ignition switch is turned to the "ON" position.

Q. Does the TPMS warning light illuminate for three seconds?

YES Go to Step 2.
NO Go to TPMS Inspection Procedure No.3 "The TPMS Warning Light does not Illuminate as a Bulb Check for Three Seconds when the Ignition Switch is Turned to the "ON" Position" (Refer to Inspection Procedure 3).
STEP 2. Using scan tool MB991958, read the diagnostic trouble code.





(1)
CAUTION:
To prevent damage to scan tool MB991958, always turn the ignition switch to the "LOCK" (OFF) position before connecting or disconnecting scan tool MB991958.

Connect scan tool MB991958 to the data link connector.
(2)Turn the ignition switch to the "ON" position.
(3)Check whether DTC C1912, C1922, C1932 or C1942 (TPMS transmitter abnormality - Tire air pressure low) is set.
NOTE:
If DTC C1912, C1922, C1932 or C1942 is set, the TPMS receiver is defective. In Step 1, the TPMS warning light illuminated for three seconds and then went out. However, the DTC is set. This means that a contradiction has arisen in the receiver operation.

Q. Is DTC C1912, C1922, C1932 or C1942 (TPMS transmitter abnormality - Tire air pressure low) set?

YES Replace the TPMS receiver (Refer to TPMS Receiver Removal and Installation). Then go to Step 8.

NO Go to Step 3.

STEP 3. Execute "Tire Pressure Sensor Check" on scan tool MB991958.

(1)Execute "Tire Pressure Sensor Check" on scan tool MB991958 for the relevant tire
(Refer to Testing and Inspection).

(2)Confirm the tire inflation pressure, which are shown on scan tool MB991958 display.
Standard value: 220kPa (32 psi)


Q. Are the tire inflation pressure displayed?

YES Go to Step 4.
NO It is judged that the TPMS could not detect low pressure due to a defective TPMS transmitter or the TPMS transmitter which is not registered is installed. Go to Step 8.
STEP 4. Check the tire pressure, which is shown on scan tool MB991958 display.

Q. Is the shown tire inflation pressure less than the threshold value (174 kPa, 25.3 psi)?

YES Go to Step 6.
NO Go to Step 5.
STEP 5. Use an accurate tire pressure gauge to measure the relevant tire inflation pressure.

Compare the actually measured value with the value shown on scan tool MB991958 to determine whether the TPMS transmitter pressure sensor is inaccurate.

Q. Is the tire inflation pressure shown on scan tool MB991958 within± 20 kPa (2.9 psi) from the actual inflation pressure?[ Ambient temperature during measurement must be 0 - 50°C (32 - 122°F)]

YES The procedure is complete.
NO Replace the TPMS transmitter of the relevant tire (Refer to TPMS Transmitter Removal and Installation).
Then go to Step 8.
STEP 6. Check the illumination condition of the TPMS warning light.

Turn the ignition switch to the "ON" position. Check that the TPMS warning light illuminates for three seconds, goes out momentarily, and then illuminates again.

Q. Does the TPMS warning light illuminate again?

YES Go to Step 7.
NO Replace the TPMS receiver (Refer to TPMS Receiver Removal and Installation). Then go to Step 8.
STEP 7. Check the relevant tire for improper inflation pressure or any other problems, and make necessary repairs. Then drive the vehicle and check if the TPMS warning light comes on.

(1)If the relevant tire has been punctured, repair it. If the valve grommet or valve core is defective, replace it (Refer to TPMS Transmitter Removal and Installation).

(2)Adjust the relevant tire inflation pressure to the value specified on the tire pressure label.

(3)Drive the vehicle, and check that the TPMS warning light goes out within 10 minutes after the vehicle speed reaches 30 km/h (19 mph).

Q. Does the TPMS warning light go out?

YES The procedure is complete. (For some reason, the TPMS transmitter could not communicate with the TPMS receiver momentarily).
NO The driving G sensor of the TPMS transmitter may be defective. Replace the TPMS transmitter of the relevant tire (Refer to TPMS Transmitter Removal and Installation). Then go to Step 8.
STEP 8. Tire pressure sensor ID registration.

Execute "Tire Pressure Sensor ID Registration" on scan tool MB991958 "Special Function"
(Refer to Tire Pressure Sensor ID Registration).

Q. Is the TPMS warning light off?

YES The procedure is complete.
NO Repeat this Step 1.