Tire Pressure Warning System - Service Information
Classification:WT04-007
Reference:
NTB04-073
Date:
June 9, 2004
LOW TIRE PRESSURE WARNING SYSTEM (LTPWS) TECHNICAL INFORMATION
APPLIED VEHICLES:
All with LTPWS
SERVICE INFORMATION
LTPWS and TPMS are the same Systems. Only the name has changed.
^ Old name: TPMS (Tire Pressure Monitor System)
^ New name: LTPWS (Low Tire Pressure Warning System)
This bulletin provides important information for the LTPWS. Use this information:
^ For correctly setting the tire air pressure.
^ When inspecting an incident vehicle or when performing a PDI.
^ When speaking to customers.
^ To help avoid LTPWS incidents and customer concerns.
Setting The Correct Tire Pressure During PDI:
^ During the PDI process, set the tire pressure to the specification shown on the Tire and Loading Information Label (placard).
^ Refer to the vehicle Owner's Manual for the placard location. For example, on the 2004 Quest, the placard is located at the bottom of the driver's side B-pillar.
^ Tire pressures should be set with the tires cold.
^ Once the tires are set to the correct pressure, confirm the following during the PDI drive check:
> The LTPWS properly operates.
> The correct tire pressure is displayed (by LTPWS).
Factors That Affect Tire Pressure: Temperature and Altitude
NOTE:
The tire pressures should be checked when the tires are COLD. The tires are considered COLD after the vehicle has been parked for 3 or more hours, or driven less than 1 mile (1.6 km) at moderate speeds.
Cold Ambient Temperatures:
^ The LTPWS measures the pressure inside the tire.
^ Cold ambient temperature conditions may cause the tire pressure to drop and the LTPWS to illuminate the Low Tire Pressure Warning Light.
Example (vehicle with a tire pressure specification of 32 p.s.i.):
^ If the temperature is 70°F and the tire pressure is 30 p.s.i., the LTPWS warning light will stay OFF.
^ However, if the temperature drops to 30°F, the tire pressure will drop to 27 p.s.i. and the LTPWS light will come ON.
If you think the LPTWS light is coming on because of temperature-related pressure changes:
^ First, check the tire pressure using the LTPWS display before replacing any parts.
^ Set the tire pressure to the correct specification. It's shown on the vehicle's Tire and Loading Information Label.
NOTE:
LTPWS does not adjust air pressure for a temperature change.
^ Please inform the customer that tire pressure can change due to temperature.
^ Cold ambient temperature conditions may effect the tire pressure more at high altitudes. See High Altitude.
High Altitude:
^ The LTPWS measures the pressure inside the tire.
^ The LTPWS does not adjust air pressure for extreme altitude conditions.
^ In extreme altitude conditions, a standard tire pressure gauge may show a different pressure than the LTPWS display.
^ The tire pressure should be set using the LTPWS display.
Example:
^ When the vehicle is at 0 ft altitude, the LTPWS display and the standard tire gauge will show the same p.s.i. reading: In this case, 30 p.s.i.
^ When the vehicle is at 5,427 ft altitude (same temperature) the LTPWS display will still show 30 p.s.i. and the standard tire gauge will show 33 p.s.i.
LTPWS Sensor Reading Times:
The tire pressure signals from the wheel sensors are updated by the control unit as follows:
^ With the vehicle stopped and ignition ON: The sensors will transmit a signal 1 time per hour.
^ Over 20 MPH: The sensors will transmit a signal 1 time per minute.
^ On command, using the transponder and the Consult "Data Monitor Screen"
Low Tire Pressure Warning Light:
^ This is a separate light that warns of low tire pressure. Complete information can be found in the vehicle Owner's Manual & Service Manual.
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