CAT Engine 2734 Fault Code: Turbo Outlet Pressure short to ground
Also called Turbo Out Press Signal Shorted to Ground, Turbo Outlet Pressure Short to Ground, Turbo Outlet Pressure Shorted to Ground, Turbo Outlservice tool Pressure short to ground, Turbocharger Outlet Pressure Sensor : Voltage Below Normal, Turbocharger Outlet Pressure Sensor Voltage Below Normal, Turbocharger Outlet Pressure Sensor voltage below normal
Turbo Outlet Pressure short to ground · ai-assisted, editor-reviewed · Last updated 2026-07-13
TL;DR
CAT code 2734 (SPN 102, FMI 4, also shown as CID 273-FMI 04 or flash code 25) means the ECM sees the turbocharger outlet (boost) pressure sensor signal drop below 0.2 VDC (some versions cite 0.5 VDC) for a set time and reads it as a short to ground. The ECM flags turbo outlet pressure as invalid data, substitutes a default pressure value, and cuts back fuel delivery, which shows up as low power. This code applies to C10, C12, C15, C16, and C27 engines.
Medium severity. The engine will keep running but will derate power because the ECM cannot trust the boost pressure reading. It will not usually strand the truck or machine immediately, but ignoring it means reduced performance and possible masking of a real boost or wiring problem underneath.
What does CAT Engine error code 2734 mean?
This code is about the turbocharger outlet pressure sensor, also called the turbo compressor outlet pressure sensor or boost pressure sensor. It tells the ECM how much pressure the turbo is putting into the intake system. The ECM uses that pressure reading to decide how much fuel to inject during acceleration, keeping the air/fuel ratio in a safe range the same way a mechanical governor would on an older engine.
Code 2734 sets when the ECM reads this sensor's signal voltage well below its normal working range, low enough to look like the signal wire has shorted to ground. Once that happens, the ECM cannot use the real pressure reading anymore. It marks turbo outlet pressure as 'Invalid Data' on the scan tool and substitutes a fixed default value instead, whether or not the actual pressure is fine.
Because the ECM no longer trusts the boost signal, it protects the engine by limiting how much fuel it will inject. The practical result the operator feels is reduced engine power and sluggish response, even though nothing may be mechanically wrong with the turbo itself. The root problem is almost always electrical, in the sensor, its wiring, or its connectors.
What triggers a CAT Engine 2734 code?
Different ECM software versions describe slightly different thresholds for this same code. Most versions call it out when the ECM reads turbo outlet pressure signal voltage below 0.2 volts for 0.24 seconds up to 1 second, with the ECM already powered up for 2 to 3 seconds. One version instead uses a threshold of below 0.5 VDC for 2 seconds. On some ECM software, the code will only set if related 5-volt supply codes (5 Volt Sensor Supply short to +batt and 5 Volt Sensor Supply short to ground) are not already active at the same time. The sensor itself runs on a regulated 5-volt supply from the ECM (about 5.0 volts, some versions state 5 ± 0.2 VDC) and normally outputs a signal between 0.2 and 4.8 VDC over an operating pressure range of 33 to 326 kPa (4.8 to 47.3 psi).
Common causes of 2734
- Damaged, corroded, or ill-fitting connectors, pins, or sockets at the sensor or ECM, including connectors not fully coupled or inserted
- Chafed, pinched, or corroded wiring in the harness between the sensor and ECM
- A short circuit in the signal wire to ground, or a short between the signal wire and the analog sensor common (return) wire
- A short between the 5-volt supply wire and the signal wire, or an open circuit in the 5-volt supply wire
- An open circuit anywhere in the sensor circuit
- A faulty or failed turbo outlet pressure sensor that needs replacement
- An incorrect sensor installed for this application
- A leak in the pressure sensing system, including a vacuum leak, or seals out of place at the sensor mounting
- Low resistance between two or more wires in the harness
- A faulty return (ground) wire for the sensor
- A defective ECM (less common, check wiring and sensor first)
- An intermittent connection problem that only shows up under vibration or temperature change
How to troubleshoot CAT Engine 2734: first checks
- Check that the sensor connector and ECM connector are fully seated, with pins and sockets free of corrosion, bending, or looseness
- Inspect the wiring harness between the sensor and ECM for chafing, pinch points, corrosion, or exposed conductors that could short to ground or to the sensor common wire
- Verify the 5-volt supply reaching the sensor and confirm it is not shorted to the signal wire or open circuited
- Back-probe the signal wire at the sensor connector with the key on and confirm voltage is within the normal operating range rather than stuck near 0.2 volts or 0.5 volts
- Check for any related active codes for the 5-volt sensor supply (short to battery or short to ground) since those can affect this reading and should be resolved first
- Inspect for physical leaks or loose seals around the turbo outlet pressure sensor and its mounting, including a vacuum leak in the sensing line
- Confirm the correct sensor part number is installed for the engine model
- If wiring and sensor test good, test sensor calibration behavior at key-on with the engine off, since the ECM calibrates these sensors during a power-up period with the engine not running
- Replace the suspect sensor if wiring and supply voltage check out, and retest before condemning the ECM
How the code clears
No separate clearing step is listed beyond fixing the underlying wiring, connector, or sensor problem. Once the fault condition is corrected and the ECM sees a normal signal voltage from the turbocharger outlet pressure sensor, the code should stop being active. Cycling the key or clearing logged codes with a diagnostic scan tool afterward is standard practice, but no dedicated reset procedure is described for 2734 itself.
Affected models and serial ranges
2734 appears in our records across 5 CAT Engine models. Match your machine by model and serial number.
| Model | Serial ranges |
|---|---|
| C10 | Serial range not listed in source records |
| C12 | Serial range not listed in source records |
| C15 | Serial range not listed in source records |
| C16 | Serial range not listed in source records |
| C27 | Serial range not listed in source records |
Frequently asked questions
What does CAT code 2734 mean?
It means the ECM detected the turbocharger outlet (boost) pressure sensor signal voltage drop low enough, below 0.2 volts or 0.5 volts depending on the software version, to be read as a short to ground. The ECM then treats boost pressure as invalid data and limits fuel to protect the engine.
Will code 2734 cause a power loss?
Yes. Once the ECM flags the turbo outlet pressure as invalid, it substitutes a default pressure value and limits fuel delivery, which is felt as reduced engine power and sluggish acceleration, even if the turbo itself is working fine.
Is code 2734 the same as SPN 102 FMI 4 or CID 273 FMI 04?
Yes. CAT fault code 2734 corresponds to SPN 102, FMI 4 on the J1939 data link and CID 273, FMI 04 on the Cat Data Link. It may also show up as flash code 25 on the diagnostic lamp.
What usually causes this code?
Most cases trace back to wiring or connector problems: corroded or loose connectors, chafed or pinched harness wiring, a short between the signal wire and ground or the sensor common wire, or an open 5-volt supply wire. A failed sensor, incorrect sensor, leak, or loose seal are also possible. A defective ECM is uncommon but listed as a last-resort cause.
Can I keep driving or operating with code 2734 active?
The engine will typically keep running, but with reduced power due to the fuel limiting response. It is not usually an immediate stop-now situation, but the underlying wiring or sensor fault should be diagnosed and repaired promptly to restore full power and rule out a bigger electrical problem.
Does this code affect other pressure sensors too?
Some ECM software versions troubleshoot this sensor using the same procedure as other analog pressure sensors, including engine oil pressure, injection actuation pressure, atmospheric pressure, and turbocharger inlet pressure sensors, since they share a similar 5-volt supply and common return wiring setup.
How do I check if the sensor itself is bad versus the wiring?
Back-probe the signal, supply, and return wires at the sensor connector with the key on. If the 5-volt supply and return are good but the signal stays low or erratic, the sensor is a likely suspect. If supply or return voltage is also abnormal, focus on the harness and connectors before replacing the sensor.