CAT Engine 1724 Fault Code: Intake Manifold Air Temp short to ground
Also called Engine Intake Manifold #1 Temperature : Voltage Below Normal, Intake Manifold Air Temp Short to Ground, Intake Manifold Air Temperature Sensor : Voltage Above Normal, Intake Manifold Air Temperature Sensor : Voltage Below Normal, Intake Manifold Air Temperature Sensor Voltage Below Normal, Intake Manifold Air Temperature Sensor Voltge Below Normal, Intake Manifold Air Temperature Sensor voltage below normal, Intake Manifold Air Temperature Sensor:Voltage Below Normal, Intake Manifold Air Temperature Sensor:Voltage Below Normal
Intake Manifold Air Temp short to ground · ai-assisted, editor-reviewed · Last updated 2026-07-13
TL;DR
CAT code 1724 (SPN 105 / FMI 4) means the ECM is reading intake manifold air temperature sensor signal voltage below 0.2 VDC, which the ECM interprets as a short to ground. The ECM substitutes a default temperature value and logs the code. It is generally a wiring or sensor issue rather than an immediate engine-damage event, but it can affect running quality.
Medium severity. This code does not usually cause immediate engine damage, but the ECM is running on a default, fixed intake manifold air temperature value instead of a real reading. That can cause poor cold running, poor acceleration under load, and smoke symptoms until the fault is fixed. Diagnose it within the shift rather than ignoring it.
What does CAT Engine error code 1724 mean?
CAT code 1724 fires when the ECM sees the intake manifold air temperature sensor's signal voltage drop below 0.2 VDC. Since this sensor should never read that low under normal operation, the ECM assumes the signal wire has shorted to ground.
When this happens, the ECM stops trusting the real sensor input and substitutes a default value for intake manifold air temperature. Depending on which version of the logic is running, that default is either 85 °C (185 °F) or 70 °C (158 °F).
The intake manifold air temperature sensor helps the ECM fine-tune fueling and timing for the actual air charge conditions going into the engine. With a default value substituted, the engine can still run, but fueling and timing decisions lose one of their real-world inputs, which is why drivability symptoms show up.
What triggers a CAT Engine 1724 code?
The ECM sets this code when signal voltage from the intake manifold air temperature sensor reads below 0.2 VDC. Depending on the ECM version, this must persist for one second (after the ECM has been powered for at least three seconds) or for eight seconds (after the ECM has been powered for at least two seconds). One version also requires that diagnostic code 0168-01 not be active before 1724 can set.
Common causes of 1724
- Connectors, pins, or sockets not fully coupled or inserted
- Corrosion, abrasion, or pinch points in the harness and wiring
- Open or short circuit in the sensor wiring
- Signal wire shorted to ground
- Short between the analog sensor common and the signal wire
- 5-volt supply wire with an open circuit
- Short between the 5-volt supply and the signal wire
- Faulty or damaged engine harness connector
- Sensor seals out of place
- Faulty intake manifold air temperature sensor, needing replacement
- Intermittent wiring harness problem
- Faulty ECM, needing replacement
How to troubleshoot CAT Engine 1724: first checks
- Inspect the intake manifold air temperature sensor connector for full seating, corrosion, or bent pins. A loose or corroded connection is one of the most common causes.
- Check the wiring harness between the sensor and the ECM for chafing, pinch points, or visible damage, especially near clamps, brackets, or areas exposed to heat.
- With the connector disconnected, check for a short to ground on the signal wire and check the sensor common line, since this fault is commonly caused by a shorted signal wire.
- Check the sensor's 5-volt supply wire (where applicable) for an open circuit or a short between the supply and signal wire.
- Test the sensor itself. If wiring and connectors check out, the sensor may be internally shorted and need replacement.
- If wiring, connectors, and the sensor all test good, the ECM itself may be at fault, though this is listed as the last-resort cause.
How the code clears
No separate clearing step is listed beyond fixing the underlying wiring, connector, or sensor fault. Once the signal voltage returns to a normal range, the ECM should stop substituting the default temperature value and the code can be cleared with a diagnostic scan tool. If equipped, the warning light will go off once the fault condition is resolved and the code is cleared.
Affected models and serial ranges
1724 appears in our records across 10 CAT Engine models. Match your machine by model and serial number.
| Model | Serial ranges |
|---|---|
| C10 | Serial range not listed in source records |
| C11 | Serial range not listed in source records |
| C12 | Serial range not listed in source records |
| C13 | Serial range not listed in source records |
| C15 | Serial range not listed in source records |
| C16 | Serial range not listed in source records |
| C175 | Serial range not listed in source records |
| C18 | Serial range not listed in source records |
| C27 | Serial range not listed in source records |
| C32 | Serial range not listed in source records |
Frequently asked questions
What does CAT code 1724 mean?
It means the ECM detected intake manifold air temperature sensor signal voltage below 0.2 VDC, which it reads as a short to ground. The ECM then uses a default temperature value instead of the real sensor reading.
Is CAT 1724 the same as SPN 105 FMI 4?
Yes. CAT 1724 corresponds to SPN 105, FMI 4 on the J1939 data link, and may also be shown as CID 172-FMI 04 on the Cat Data Link or as a 38 flash code on the diagnostic lamp.
Can I keep driving or running the engine with code 1724 active?
The engine will typically keep running since the ECM substitutes a default value, but you may notice poor stability, poor cold running, poor acceleration under load, and white or black smoke. It is best to diagnose the fault promptly rather than run on the default value long-term.
What's the most common cause of this code?
Connector and wiring issues are the most frequently listed causes: connectors not fully seated, corrosion, chafed wiring, or a signal wire shorted to ground. A faulty sensor or ECM is possible but less common.
What default temperature value does the ECM use once this code is active?
Depending on the ECM software version, the ECM substitutes either 85 °C (185 °F) or 70 °C (158 °F) for intake manifold air temperature while the code is active.
Does this code affect other temperature sensors on the engine?
The troubleshooting procedure is similar for other two-terminal temperature sensors like engine coolant temperature and engine oil temperature sensors, since they share the same sensor common circuit design, but code 1724 itself is specific to the intake manifold air temperature sensor.
Will this code clear itself?
No. The signal voltage has to return to a normal range and stay there. There's no automatic reset described beyond repairing the wiring, connector, or sensor and then clearing the code with a diagnostic scan tool.