Cummins fault code 691
Turbocharger 1 Compressor Intake Temperature Circuit: circuit voltage high / shorted high
What it means
Cummins' description: Turbocharger 1 Compressor Intake Temperature Circuit - Voltage above normal, or shorted to high source.
SPN 1172 is Engine Turbocharger 1 Compressor Intake Temperature. 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.
The turbocharger forces air into the engine. Most modern Cummins engines use a variable geometry turbo (VGT) with an electronic actuator. The ECM watches intake manifold pressure, turbo speed and compressor temperatures to control boost.
What the lamp means
An amber (yellow) warning lamp means the engine can usually keep running, but the fault should be repaired soon, ideally the same day.
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 brief underboost code climbing a hill that clears, with normal power the rest of the time.
Schedule a repair
Noticeable power loss, black smoke, or amber lamp with a boost or VGT code. Get it checked. Boost leaks and sticky VGT actuators get worse and hurt fuel economy.
Stop and get help
Loud whine or grinding from the turbo, heavy smoke, oil pouring out of the exhaust, or a stop lamp. Shut it down. A failing turbo can feed parts or oil into the engine.
Common causes
FMI 3 is an electrical or signal fault, so start with the circuit:
- VGT actuator internal fault or wiring problem (common)
- Boost or intake manifold pressure sensor failed or plugged
- Turbo speed sensor or wiring fault
- Actuator power, ground or network connection problem
If the circuit checks out, the reading may be real. Other possibilities: boost leak: split charge air hose, loose clamp, cracked charge air cooler; vGT vanes sticking from soot; worn or damaged turbo.
What you can check before calling
- Listen for a new hiss or whistle under load, a typical sign of a boost leak
- Check charge air hoses and clamps for oil or soot
- Check the air filter restriction indicator
- Notice whether power loss happens only under heavy load or on hills
Clearing the code without fixing the cause usually brings it right back, and on emissions systems it can restart derate timers.
Engines and sources
Listed by Cummins for: QSB 6.7, QSL 9, QSX 15, QSB 4.5, QSF 3.8, QSG 12. 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: Cummins Tier 4 Fault Codes. Always confirm with Cummins service information (QuickServe) for your engine serial number.
Same SPN, other failure types
- 617 SPN 1172 FMI 0
High Turbo Compressor Inlet Temp LB: reading above normal (most severe) - 692 SPN 1172 FMI 4
Turbocharger 1 Compressor Intake Temperature Circuit: circuit voltage low / shorted low - 693 SPN 1172 FMI 2
Turbocharger 1 Compressor Intake Temperature: erratic or intermittent signal - 3369 SPN 1172 FMI 9
Turbocharger 1 Compressor Intake Temperature Sensor: abnormal update rate - 3371 SPN 1172 FMI 19
Turbocharger 1 Compressor Intake Temperature Sensor: network data error
Related Turbo, VGT and boost codes
- 694 SPN 1173 FMI 3
RBF Turbo Comp Inlet Temp Sens Failed High: circuit voltage high / shorted high - 687 SPN 103 FMI 18
Turbocharger 1 Speed: reading below normal (moderately severe) - 695 SPN 1174 FMI 4
RBR Turbo Comp Inlet Temp Sens Failed Low: circuit voltage low / shorted low - 686 SPN 103 FMI 2
Turbocharger 1 Speed: erratic or intermittent signal - 741 SPN 1176 FMI 3
Turbocharger 1 Compressor Intake Pressure Circuit: circuit voltage high / shorted high - 742 SPN 1176 FMI 4
Turbocharger 1 Compressor Intake Pressure Circuit: circuit voltage low / shorted low
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 691 mean?
Cummins fault code 691 is J1939 SPN 1172 FMI 3: Turbocharger 1 Compressor Intake Temperature Circuit - Voltage above normal, or shorted to high source. In plain terms: turbocharger 1 compressor intake temperature circuit: circuit voltage high / shorted high.
Can I keep driving with Cummins code 691?
Usually for a short time, if the engine runs normally and no other warnings are on. Get it diagnosed soon, because many amber codes lead to a derate if ignored. Look at the green, yellow and red examples on this page to judge your situation.
What is the SPN and FMI for Cummins code 691?
SPN 1172 identifies the part or system (Engine Turbocharger 1 Compressor Intake Temperature). FMI 3 describes the type of failure: circuit voltage high / shorted high.
What usually causes Cummins code 691?
The most common causes are: vGT actuator internal fault or wiring problem (common); boost or intake manifold pressure sensor failed or plugged; turbo speed sensor or wiring fault.
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