Cummins fault code 128
Right Bank Intake Manifold Pressure Sensor Circuit Failed High: circuit voltage high / shorted high
What it means
Cummins' description: Right Bank Intake Manifold Pressure Sensor Circuit Failed High.
SPN 1129 is Right Bank Intake Manifold Pressure Sensor Circuit Failed High. FMI 3 means the voltage on the circuit is higher than possible for a good sensor, usually an open signal wire, a short to a power wire, or a failed sensor.
These sensors measure the air coming into the engine: intake manifold temperature, charge air cooler outlet temperature, ambient temperature, barometric pressure, humidity and air filter restriction. The ECM uses them to calculate fueling and timing.
What the lamp means
This code normally doesn't turn on a dash lamp. It's logged in the ECM for a technician to see, and often explains another active code.
Green, yellow, red: three ways this can look
The same code can be a quick fix or a reason to shut down. Match your situation to the closest example.
Keep an eye on it
A one-time sensor code with normal power and temperatures.
Schedule a repair
Amber lamp, rough cold starts, or the code returns. Usually a sensor or connector. Book it so fueling stays correct.
Stop and get help
Several sensor codes at once with a stop lamp or no-start. That can point to a shared sensor supply or ECM problem. Get it diagnosed before driving.
Common causes
FMI 3 is an electrical or signal fault, so start with the circuit:
- Sensor connector corroded or loose
- Harness damage
- Failed sensor
- Shared 5-volt sensor supply problem (several sensor codes at once)
If the circuit checks out, the reading may be real. Other possibilities: clogged air filter; dirty or blocked charge air cooler or radiator fins; real high intake temperature in hot weather or under heavy load.
What you can check before calling
- Check the air filter and the restriction indicator
- Clean bugs and debris from the front of the charge air cooler
- Look for unplugged or damaged connectors on intake sensors
Clearing the code without fixing the cause usually brings it right back, and on emissions systems it can restart derate timers.
Engines and sources
Cummins uses the same fault code numbers across its electronic engines, including on-highway models like the ISB/B6.7, ISL/L9 and ISX/X15, though not every code applies to every engine or software level. Source: Diagnostic Fault Codes for Cummins Engines. Always confirm with Cummins service information (QuickServe) for your engine serial number.
Same SPN, other failure types
- 126 SPN 1129 FMI 16
High Intake Manifold Pressure Right Bank: reading above normal (moderately severe) - 127 SPN 1129 FMI 18
Low Intake Manifold Pressure Right Bank: reading below normal (moderately severe) - 129 SPN 1129 FMI 4
Right Bank Intake Manifold Pressure Sensor Circuit Failed Low: circuit voltage low / shorted low
Related Intake air and environment sensors codes
- 153 SPN 105 FMI 3
Intake Manifold 1 Temperature Sensor Circuit: circuit voltage high / shorted high - 154 SPN 105 FMI 4
Intake Manifold 1 Temperature Sensor Circuit: circuit voltage low / shorted low - 155 SPN 105 FMI 0
Intake Manifold 1 Temperature: reading above normal (most severe) - 156 SPN 1131 FMI 3
Left Bank Rear Intake Manifold Temp Sensor Circuit Failed High: circuit voltage high / shorted high - 157 SPN 1131 FMI 4
Left Bank Rear Intake Manifold Temp Sensor Circuit Failed Low: circuit voltage low / shorted low - 158 SPN 1131 FMI 0
High Intake Manifold Temp: reading above normal (most severe)
Look up another code
Cummins fault code (like 1922), J1939 SPN and FMI (like SPN 3251 FMI 0), or an OBD-II code (like P0420).
Questions
What does Cummins fault code 128 mean?
Cummins fault code 128 is J1939 SPN 1129 FMI 3: Right Bank Intake Manifold Pressure Sensor Circuit Failed High. In plain terms: right bank intake manifold pressure sensor circuit failed high: circuit voltage high / shorted high.
Can I keep driving with Cummins code 128?
Usually, yes. This code doesn't normally turn on a lamp by itself, but check for other active codes that might be more serious. Look at the green, yellow and red examples on this page to judge your situation.
What is the SPN and FMI for Cummins code 128?
SPN 1129 identifies the part or system (Right Bank Intake Manifold Pressure Sensor Circuit Failed High). FMI 3 describes the type of failure: circuit voltage high / shorted high.
What usually causes Cummins code 128?
The most common causes are: sensor connector corroded or loose; harness damage; failed sensor.
Diesel down in the Midlands?
We work on Cummins-powered pickups, vans and medium-duty trucks across Lexington, Columbia and the Midlands, on site at your yard or roadside.