Applicability basis: Authorized vehicle records confirm Ram 1500 Classic Truck 4WD applications with the 5.7-liter gasoline engine at the 2019 and 2024 endpoints. Detailed system operation and diagnostic evidence for this overview was verified on the 2019 application. Exact sensor locations, module routing, circuit identifiers, thresholds, test values, scan-tool functions, and service procedures can vary by model year, drivetrain, equipment, and calibration; use current service information for the truck being repaired.
What the air-temperature sensing system does
The engine and body control systems need credible temperature information before they can interpret airflow, fuel demand, cold-start behavior, climate operation, and several rationality checks. On this application, two air-temperature measurements matter to the related DTCs:
- the ambient air temperature (AAT) sensor reports the air around the vehicle; and
- the intake air temperature (IAT) sensor reports the temperature of air entering the engine.
They describe different environments and use separate diagnostic paths. AAT can influence displayed outside temperature and body-side functions while also contributing to powertrain plausibility checks. IAT helps the powertrain control module (PCM) interpret incoming-air density and operating conditions. One sensor is not a substitute for the other.
A temperature-sensor DTC means the monitored electrical signal or comparison failed its calibrated test. It does not prove that the weather is unusually hot or cold, and it does not automatically prove that the sensor itself has failed.
How the system turns temperature into usable data
The sensing element changes electrically with temperature
Automotive air-temperature sensors commonly use a temperature-sensitive resistor. The control circuit supplies a reference through an internal pull-up path and watches the returned signal. As sensor resistance changes, signal voltage changes. The module converts that electrical value into a temperature estimate.
That relationship makes circuit integrity part of the measurement. An open wire, excessive resistance, short to ground, short to voltage, poor terminal contact, damaged sensor ground, or internal sensor fault can imitate an extreme temperature even when the air itself is normal.
AAT represents the vehicle's outside-air context
The AAT path is a body-side measurement that is shared with the powertrain strategy. Depending on configuration, the exact sensor location, intermediate module, and circuit routing can differ. The PCM ultimately needs a credible ambient value, but diagnosis must follow the wiring and module path shown for the truck rather than assuming the sensor is wired directly to the PCM.
IAT represents the engine's incoming-air context
The IAT sensor measures the air entering the engine. Its signal and sensor-ground paths are monitored by the PCM. Heat soak after shutdown, engine-compartment temperature, airflow, load history, and actual ambient conditions can all make IAT differ from AAT during normal operation.
Cold-start comparison checks plausibility
After a sufficient soak, AAT, IAT, and engine coolant temperature should begin in a reasonably related region. The monitoring strategy can compare the three after start and, when required, compare them again after a short drive. Agreement between two sensors can help identify which third reading is implausible.
This is a plausibility check, not a rule that all three values must always match. Once the engine runs, coolant warms and intake temperature responds to airflow and underhood heat, so operating context matters.
What the related DTCs are telling you
| DTC | Diagnostic direction | What it directs you to prove |
|---|---|---|
| P0072 | AAT circuit signal is electrically at the low side of the monitored range | Whether a shorted circuit, sensor/ground interaction, connector fault, AAT sensor, or responsible module explains the signal |
| P0073 | AAT circuit signal is electrically at the high side of the monitored range | Whether an open or high-resistance path, short to voltage, sensor-ground fault, AAT sensor, connector, or responsible module explains the signal |
| P0113 | IAT Sensor 1 circuit signal failed its high-circuit monitor | Whether the IAT signal path, sensor ground, connector, sensor, or PCM is responsible in the directed order |
The words “low” and “high” describe the monitored circuit condition, not a confirmed air temperature and not a replacement instruction. P0072 and P0073 point to the AAT path. P0113 points to the IAT path. Multiple temperature, system-voltage, or communication codes may indicate a shared electrical or module problem that should be diagnosed before individual sensors.
What the driver or technician may notice
Possible observations include:
- a malfunction indicator lamp with little or no drivability complaint;
- an outside-temperature display that is implausible, fixed, delayed, or intermittent;
- an IAT scan value that appears implausibly hot or cold for the soak and operating condition;
- altered cold-start behavior, fuel correction, or response because a substitute value is being used;
- a fault that appears after mirror, door, front-end, intake, air-cleaner, harness, battery, or module work;
- several temperature readings that disagree after a true cold soak.
Symptoms are clues, not failure proofs. Heat soak can make IAT warmer than AAT. Sun load, road heat, slow vehicle speed, sensor placement, and recent operation can affect AAT. Compare values only under conditions where the comparison is meaningful.
Common failure categories
Open or high-resistance circuits
A broken conductor, backed-out terminal, corrosion, weak splice, damaged connector lock, or partially separated wire can move a temperature signal toward an electrical extreme. Vibration and temperature can make the fault intermittent. A visual inspection alone does not prove that the circuit can carry the intended signal.
Shorts to ground or voltage
Rubbed insulation, pinched wiring, water intrusion, incorrect previous probing, or contact with another circuit can pull the signal out of range. Use the exact diagram to isolate every connected component before continuity or short testing so the test does not mistake a normal internal path for a harness fault.
Sensor-ground faults
The signal is meaningful only relative to its proper sensor ground. An open, excessive resistance, poor terminal, or cross-connection in the ground path can shift the reported value. Do not substitute a convenient chassis ground unless the current procedure specifically directs it.
Connector and terminal problems
Loose engagement, spread terminals, pushed-back pins, damaged seals, water entry, corrosion, or oversized test probes can create or worsen an intermittent fault. Inspect both connector halves and preserve terminal tension.
Sensor condition or installation
The sensing element may be electrically faulty or physically damaged. The IAT sensor can also be affected by contamination or intake-system work. The AAT sensor and its harness can be affected by body, mirror, door, or front-end work depending on configuration. Confirm the actual location and routing before disturbing components.
Module, power, or network responsibility
The module that reads or relays the sensor value can be involved, but it belongs near the end of the diagnostic path. Resolve active system-voltage and communication DTCs first, then prove powers, grounds, circuits, terminals, and sensor response before considering module replacement or programming.
A practical system-first diagnostic strategy
1. Preserve the original evidence
Confirm the exact year, engine, drivetrain, equipment, calibration, recent repairs, and current service information. Save the complete module scan, active/pending/history DTCs, freeze-frame or failure-record data, and relevant AAT, IAT, coolant-temperature, voltage, and operating-condition data before clearing anything.
2. Check code relationships before parts
Look for system-voltage, communication, sensor-reference, or several temperature-sensor codes. A shared supply, ground, connector, module, or network issue can produce more than one implausible value. Diagnose the highest-priority shared fault first.
3. Compare temperature values under valid conditions
After a genuine cold soak, compare AAT, IAT, and coolant temperature with the truck's actual environment. Do not condemn a sensor from a hot restart or a sun-heated parked vehicle. After startup, watch whether each value changes in a direction that makes physical sense.
4. Decide whether the fault is active or intermittent
If the code is active, follow the current directed circuit test. If it is not active, use the stored conditions to reproduce it safely while inspecting and gently stressing the relevant harness and connectors. A value that changes with harness movement is evidence, but the precise terminal or conductor still must be isolated.
5. Inspect before disconnecting everything
Check recent work areas, harness routing, retainers, sharp edges, heat exposure, water entry, connector locks, seals, and terminal position. Photograph routing before disassembly. Avoid creating a second fault while searching for the first.
6. Prove signal and sensor-ground paths
Use the exact wiring diagram, module path, terminal-safe adapters, and specified test conditions. Check for opens, excessive resistance, shorts to ground, shorts to voltage, and cross-circuit contact in the order directed by current service information. Disconnect modules and components only as instructed before resistance testing.
7. Prove sensor response before controller responsibility
A directed substitution or jumper test can show whether the reading module recognizes a known circuit state. That test proves the response of the path; it is not permission to leave a jumper installed. Replace the sensor only when circuit integrity and the directed response support it. Consider a module only after its powers, grounds, connectors, communication, and related circuits are proven.
8. Verify the complete repair
Restore routing, seals, locks, retainers, intake joints, and removed components. Clear codes when directed, repeat the relevant self-test or operating condition, and confirm that the code does not return as pending or confirmed. Recheck temperature plausibility after an appropriate soak and verify any display or drivability complaint.
A cleared warning lamp or one plausible scan value during a brief idle is not repair verification.
Repair categories
The confirmed result may support one or more of these repair categories:
- repair or replacement of damaged signal or sensor-ground wiring;
- terminal, connector, seal, splice, or harness-routing repair;
- AAT sensor replacement when the AAT circuit and module response are proven;
- IAT sensor replacement when the IAT circuit and PCM response are proven;
- correction of intake-system damage or a disturbed sensor installation;
- body-side or powertrain module repair, replacement, and programming only after all prerequisites are met;
- correction of a shared voltage, ground, or communication fault that affected several readings.
Do not choose the repair category from the code title alone.
Safety and service cautions
Running-engine tests place the technician near the fan, belts, pulleys, hot exhaust parts, and other moving or hot components. Secure clothing, hair, leads, and tools, and keep hands out of the fan and belt paths. Do not route meter leads where they can be caught when the engine starts.
Turn the ignition off and follow the current procedure before disconnecting modules or checking continuity. Never measure resistance on an energized circuit. Use terminal-safe adapters and do not force oversized probes into sensor or module connectors. Restore weather seals and retainers so the repair does not create a future water-entry or chafing fault.
Final takeaway
The 2019-2024 Ram 1500 Classic 5.7L HEMI Gas air-temperature sensing system uses separate ambient and intake measurements, then evaluates them in electrical and operating context. AAT gives the vehicle an outside-air reference; IAT describes the air entering the engine; coolant temperature provides another comparison point during cold-start plausibility monitoring.
P0072, P0073, and P0113 identify failed circuit checks, not automatically failed sensors and not confirmed real-world temperature extremes. Preserve the original evidence, check related voltage and communication codes, compare values only under valid conditions, inspect routing and terminals, prove both signal and sensor-ground paths, and move to sensor or controller responsibility only when directed test results support it. Finish by reproducing the relevant monitor and confirming that the readings, DTC state, and original complaint are all resolved.
