CAT Engine SPN3563FMI3 Fault Code: Engine Intake Manifold #1 Absolute Pressure : Voltage Above Normal
Engine Intake Manifold #1 Absolute Pressure : Voltage Above Normal · ai-assisted, editor-reviewed · Last updated 2026-07-13
TL;DR
SPN 3563 FMI 3 means the CAT ECM sees the intake manifold pressure sensor signal above 4.8 VDC for at least 2 seconds after the ECM has been powered for 2 seconds. The ECM treats the reading as invalid, substitutes a default pressure value, and on engines with an electronic wastegate, defaults the wastegate solenoid current. Expect poor acceleration until the fault clears.
Medium severity. The engine keeps running but the ECM forces a default intake manifold pressure and, on electronic wastegate engines, a default wastegate solenoid current. This is done specifically to prevent turbocharger overspeed from overpressuring the intake manifold. Poor acceleration is the main symptom, so it should be diagnosed promptly, but it is not an immediate stop-engine situation.
What does CAT Engine error code SPN3563FMI3 mean?
SPN 3563 FMI 3 is a CAT code for the Engine Intake Manifold #1 Absolute Pressure sensor circuit reading voltage above normal. The intake manifold pressure sensor tells the ECM how much boost pressure the turbocharger is producing so the ECM can manage fueling, timing, and (on some engines) the electronic wastegate.
When the signal voltage climbs above 4.8 VDC for at least 2 seconds, with the ECM already powered for 2 seconds, the ECM decides the sensor signal is no longer trustworthy. It flags the intake manifold pressure as invalid and substitutes a maximum valid pressure value for 2 seconds, then continues using a default value.
On engines with an electronically controlled wastegate, the ECM also forces the wastegate solenoid current to a default setting while the code is active. This default is intentional: it is meant to stop any intake manifold overpressure that could result from a turbocharger overspeed. The tradeoff is that the engine will have poor acceleration until the fault is resolved.
What triggers a CAT Engine SPN3563FMI3 code?
The ECM sets this code when the intake manifold pressure sensor signal voltage is above 4.8 VDC for at least 2 seconds, and only after the ECM itself has been powered for 2 seconds.
Common causes of SPN3563FMI3
- Damaged connectors and/or wiring at the intake manifold pressure sensor or its harness
- A problem with the wiring harness itself, including chafing, pinching, or corrosion
- An intermittent electrical problem in the circuit that comes and goes
- A faulty intake manifold pressure sensor
- The latest ECM flash file not installed (older software revision)
- A faulty ECM
How to troubleshoot CAT Engine SPN3563FMI3: first checks
- Inspect the intake manifold pressure sensor connector and mating harness connector for corrosion, bent pins, moisture, or looseness
- Trace the sensor wiring for chafing, pinched sections, or damage against the manifold, turbo, or engine components
- Check for a short to a higher voltage source or an open condition in the signal circuit that would push the reading above 4.8 VDC
- Verify the ECM has the latest flash file installed for this engine, since an outdated flash file is a listed cause
- Wiggle-test the harness and connectors while monitoring the sensor signal for intermittent voltage spikes
- If wiring and connectors check good, test or swap the intake manifold pressure sensor itself before condemning the ECM
How the code clears
No separate clearing step is listed. Once the underlying wiring, connector, sensor, or flash file issue is corrected and the signal voltage stays within normal range, the code should stop being active on the next monitored cycle. Confirm with a diagnostic tool that the code is no longer active and that intake manifold pressure readings track normally during operation.
Frequently asked questions
What does SPN 3563 FMI 3 mean on a CAT engine?
It means the ECM detected the intake manifold pressure sensor signal voltage above 4.8 VDC for at least 2 seconds, which it reads as a voltage-above-normal fault on that circuit.
Can I keep operating the machine with this code active?
The engine will typically keep running, but expect poor acceleration because the ECM is using a default intake manifold pressure value and, on electronic wastegate engines, a default wastegate solenoid current. It is best to get it diagnosed rather than run it indefinitely.
Is this code caused by a bad sensor or bad wiring?
It can be either. Listed causes include damaged connectors and wiring, a harness problem, an intermittent electrical issue, a faulty sensor, an outdated ECM flash file, or a faulty ECM.
Why does the engine lose power when this code is active?
The ECM defaults the wastegate solenoid current on electronically controlled wastegate engines specifically to prevent intake manifold overpressure from a turbocharger overspeed. That default setting causes the poor acceleration.
Does updating the ECM software fix this code?
An outdated flash file is one of the listed causes, so checking that the ECM has the latest flash file installed is a valid step before replacing parts.
Will the code clear itself once the wiring is fixed?
No separate clearing step is documented. Once the voltage condition is corrected, the code should stop being active on the next cycle; confirm with a diagnostic tool.