How to Read Your TPMS Display: Pressure Readings, Temperature Data, and Alarm Codes Explained

How to Read Your TPMS Display: Pressure Readings, Temperature Data, and Alarm Codes Explained

How to read your TPMS display — pressure, temperature, and alarm codes explained

Grundig Auto  ·  TPMS User Guide

How to Read Your TPMS Display:
Pressure Readings, Temperature Data, and Alarm Codes Explained

Installing a TPMS is the first step. Understanding what it's telling you is the step most drivers skip. This guide covers everything the display is showing — and what to do about it.

A TPMS display showing readings from six tire positions generates more information than most drivers know how to use. The pressure numbers are straightforward enough — but what does a temperature reading of 155°F mean for a highway drive? How much below the alarm threshold can a tire drop before it matters at low speed vs high speed? When two alarms fire simultaneously on different positions, which one demands immediate action and which one can wait for the next rest stop? The complete Grundig TPMS range monitors both pressure and temperature for every tire position simultaneously — and getting the most from that monitoring requires understanding what each reading type represents and how to interpret combinations of readings together rather than in isolation.

This guide covers every data type displayed by a TPMS system, the correct interpretation of each alarm type, how to set threshold values that produce useful warnings rather than constant false alarms, and the standard response protocol for each alarm scenario. Most of this information is not in the product manual — it requires understanding how tire pressure physics relates to the numbers on the screen.




Reading Types

Pressure vs Temperature: What Each Number Is Actually Telling You

Pressure Reading — PSI or Bar

What it measures and what it means

Pressure readings show gauge pressure — the difference between internal tire pressure and atmospheric pressure at the sensor's location. This number changes with temperature (approximately 1 PSI per 10°F), altitude (approximately 0.5 PSI per 1,000 feet of altitude gain), and load (pressure rises slightly as the tire deforms under weight). A "correct" pressure reading is one that falls within the range appropriate for the tire's current temperature, load, and altitude conditions — not simply a fixed number regardless of operating environment.

Temperature Reading — °F or °C

The early warning that pressure misses

Temperature readings show the air temperature inside the tire cavity, which reflects both ambient conditions and heat generated by tire flex. A tire generating excess heat from underinflation, overloading, brake heat transfer, or an internal defect will show elevated temperature before the heat affects pressure enough to trigger a pressure alarm. Temperature is the early warning signal — a tire running significantly hotter than the others on the same vehicle in the same conditions warrants investigation even if pressure appears normal.

Which reading to check first when conditions change: At highway speed in normal conditions — monitor pressure. When descending a long mountain grade — check temperature, since brake heat transfers into tires and may push temperature above safe limits before pressure alarms. During a summer afternoon drive — watch both simultaneously, as heat from ambient temperature and friction can push pressure toward the high threshold while also elevating temperature. After parking on a hot surface — temperature will be elevated but will normalise quickly once moving; pressure will stabilise more slowly.



Setting Thresholds

How to Configure Alarm Values That Work in Real Conditions

Factory-default alarm thresholds are calibrated for passenger car configurations at typical passenger car pressures. For RV owners and commercial truck operators running pressures of 80 to 120+ PSI, these defaults are almost always wrong — set either too low (generating false alarms during normal heat buildup) or too high (failing to alarm when actual underinflation develops). Configuring thresholds correctly requires understanding what "correct" means for your specific vehicle, load, and operating environment.

Low Pressure Alarm Threshold

Set to 15–20% below the correct cold inflation for your maximum loaded weight. For a tire requiring 100 PSI when fully loaded, set the low-pressure alarm at 80–85 PSI. This provides meaningful warning before the underinflation becomes dangerous, while avoiding alarms triggered by normal cold-morning pressure variation or altitude effects. Do not set this threshold at the cold inflation specification — normal operating temperature will push pressure above the alarm level within 30 minutes, generating constant false alarms.

High Pressure Alarm Threshold

Set to 15% above the correct cold inflation for summer operation. For a 100 PSI cold specification, set the high alarm at 114–115 PSI. This catches genuine overinflation events — which occur when heat stack (ambient + friction + solar) pushes pressure beyond the tire's structural comfort zone — while not alarming on the normal pressure rise from cold start to operating temperature. This alarm is critical in summer and often not configured by drivers who focus only on low-pressure protection.

High Temperature Alarm Threshold

Most commercial tire manufacturers specify a maximum operating temperature of 200–220°F for the tire interior. Set the high temperature alarm at 175–185°F — providing warning before the structural limit is approached. A tire at 190°F is operating outside its designed thermal range; a tire at 160°F after a long mountain descent is elevated but within normal range. Context matters: a consistently hot tire is a problem; a briefly elevated temperature on a specific drive segment requires judgment rather than immediate action.

Rapid Pressure Loss Alarm

This threshold should be pre-set by the manufacturer and typically triggers when pressure drops more than 20% in a short time window — indicating a sudden loss event rather than gradual leakage. Unlike the other thresholds, this one should not require user configuration. If the system is generating rapid-loss alarms without corresponding physical events, check sensor battery status and valve stem integrity before adjusting the threshold.




Alarm Response Guide

The Correct Action for Every Alarm Type

Low Pressure — Single Position
Gradual pressure loss — slow leak or underinflation Reduce speed. Monitor the reading — if pressure is continuing to drop rapidly, pull over immediately. If the pressure is stable at a low level, proceed to the next safe exit or rest area and inspect. Check for nail puncture, valve stem condition, and correct inflation. Do not continue at highway speed on a significantly underinflated tire. Immediate attention — reduce speed now
Low Pressure — Multiple Positions Simultaneously
Temperature drop, altitude change, or sensor calibration issue Multiple positions alarming simultaneously with gradual pressure loss typically indicates a temperature-related pressure drop (overnight cold, elevation change) or a sensor calibration drift rather than multiple simultaneous punctures. Cross-check with a physical gauge at the next stop. If readings match the gauge and are within normal range for current conditions, adjust thresholds. If readings are genuinely low across all positions, inflate to specification before departing. Check at next opportunity — cross-verify with gauge
High Pressure — Single Position
Heat buildup in one tire — brake heat, sun exposure, or friction A single position showing high pressure while others are normal suggests localized heat — most commonly from a dragging brake, a bearing issue, or a position in direct sun exposure while others are shaded. Reduce speed and stop when safe. Allow the affected position to cool. Do not release air from a hot tire — check pressure after cooling and correct only if cold pressure is above specification. Stop when safe — check for brake or bearing issue
High Pressure — All Positions
Summer heat stack — normal physics, not a failure All positions rising simultaneously to near or above the high threshold is the expected result of combined ambient heat, solar radiation, and friction heat on a summer drive. Reduce speed to lower friction heat generation. Stop in shade if available and allow tires to cool. Do not release air — the pressure will drop as tires cool and you will be underinflated on re-departure. Adjust future cold inflation slightly lower if this is occurring consistently on normal drives. Reduce speed — cool before releasing any air
High Temperature — Single Position
Abnormal heat generation — the most important alarm to act on quickly A single position running significantly hotter than the others — even with normal pressure — indicates a localised problem: internal tire damage, a brake component generating heat, an overloaded axle position, or sustained underinflation for the actual load being carried. This alarm warrants more urgency than a pressure alarm because the condition causing it may not yet have manifested as a pressure deviation. Stop and inspect the affected position. Highest priority — stop and inspect immediately
Rapid Pressure Loss
Sudden air loss event — puncture or valve failure Reduce speed immediately and smoothly — do not brake hard on a rapidly deflating tire. Signal and move to the shoulder safely. The rapid-loss alarm distinguishes between a slow leak and a sudden breach; this alarm means the tire is losing significant pressure quickly and the window for controlled action is short. Do not continue driving on a rapidly deflating tire at any speed. Emergency — decelerate immediately and pull over
Sensor Low Battery
Battery approaching end of life — plan replacement The sensor is still functioning and transmitting valid readings. This is a forward warning — the sensor will continue providing accurate data for weeks to months, depending on transmission frequency and temperature. Plan sensor replacement within the next service interval. Do not ignore this alarm: when the battery is fully depleted, the position drops off the display entirely with no further warning. Plan replacement within next service interval
Signal Loss — Position Dropout
Sensor dead or disconnected — this position is unmonitored A position that disappears from the display entirely is no longer being monitored. The sensor may have completely depleted its battery, been physically damaged, or lost its pairing. This is not a "no news is good news" situation — the tire in this position is receiving zero monitoring coverage. Inspect the sensor and valve stem at the next stop, and do not assume the tire is fine simply because no alarm has been received. Investigate at next stop — position unmonitored
Grundig RV TPMS display — all tire positions shown simultaneously with pressure and temperature
5.0" display showing all monitored positions simultaneously — pressure and temperature for each, with position labeling clear enough to read at a glance while driving



Normal Reading Ranges

What to Expect at Different Points in a Typical Drive

Reference ranges for a correctly configured system:

Pre-departure (cold tires): Pressure should match gauge reading ±1–2 PSI. Temperature should be near ambient air temperature. Any position more than 3 PSI different from others warrants investigation before departure.

30 minutes at highway speed: Pressure 4–7 PSI above cold reading. Temperature 40–60°F above ambient. All positions should be rising at similar rates — a position that isn't warming as expected may have insufficient inflation for its load.

Peak summer highway (2–4 hours): Pressure 8–12 PSI above cold reading. Temperature up to 80°F above ambient in extreme conditions. High-pressure alarm may approach if summer heat stack is severe — correct response is to reduce speed, not release air.

After mountain descent: Temperature may be 20–40°F above pre-descent reading from brake heat transfer. Allow 20–30 minutes of normal driving for temperature to normalise before interpreting readings as representative of tire condition.

The Complete Range

RV & Motorhome

Grundig RV TPMS

116 PSI, 4/6/8-wheel. 5.0" display showing all positions. Pressure + temperature per position. Full alarm suite with configurable thresholds. $119.

$119

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Dually Trucks

Solar TPMS 6-Wheel

6 positions including inner duals. Solar powered. 6 alarm types. All readings individually reported — no averaging between inner and outer dual positions.

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Heavy Commercial

Grundig S08 TPMS

218 PSI ceiling, 8/12-wheel. Designed for Class A diesel and heavy commercial where pressure ranges require a system calibrated for high-pressure operation. $259.

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Every reading, every position, explained — and monitored. Free shipping on all systems  ·  From $119

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