CAT Engine 2835 Fault Code: Filter Restrict Lamp open/short to +batt
Also called Filter Restrict Lamp Open/Short to Batt+, Filter Restriction Lamp Open/Short to Batt+
Filter Restrict Lamp open/short to +batt · ai-assisted, editor-reviewed · Last updated 2026-07-13
TL;DR
CAT fault code 2835 means the ECM detected a short to battery positive or an open circuit in the Air Filter Restriction Lamp wiring (wire 430-BU), after the ECM has been powered for at least 2 seconds. This is a lamp circuit fault, not an actual air restriction fault, though it affects the ECM's ability to warn you if a restriction happens.
Medium severity. The engine itself is not derated by this code. The real risk is that the Air Filter Restriction Lamp circuit is broken, so if the engine actually develops an air intake restriction later, you may not get a visual warning. Diagnose within the shift rather than ignoring it long term.
What does CAT Engine error code 2835 mean?
The Air Filter Restriction Lamp tells the operator when the engine's air filters are clogged or intake airflow is otherwise restricted. The ECM figures this out by comparing pressure readings from the Atmospheric pressure sensor and the Turbo Compressor Inlet pressure sensor. If those two readings disagree by enough, the ECM lights the lamp and can derate engine power.
Code 2835 is different from an actual restriction event. It fires when the ECM tries to energize the lamp circuit itself and finds a problem: either the circuit is open (no path for current) or it is shorted to battery positive. One side of the lamp gets 24 volt DC from the ECM when the lamp should be on, and the other side connects to a digital return wire.
Because this is a lamp-circuit fault, the engine's air filter restriction detection logic (the pressure comparison and any related derate) is separate from this code. 2835 just tells you the warning lamp wiring is not working correctly, so the driver may not see a warning even if a real restriction later occurs.
What triggers a CAT Engine 2835 code?
The ECM sets this code when it detects low current or an open condition in the lamp circuit (wire 430-BU), consistent with a possible short to battery positive, after the ECM has been powered up for at least 2 seconds. In some versions this is described as the ECM trying to turn the lamp on but not seeing enough current draw to confirm the bulb lit.
Common causes of 2835
- Bad or burned out lamp bulb
- Damaged, corroded, or loose connectors and wiring in the lamp circuit
- Wire 430-BU shorted to ground or to power somewhere in the engine or machine harness
- Wire 430-BU shorted to ground specifically through wires 993-BR, 998-BR, or 229-BK
- Wire 430-BU shorted to power specifically through wires 150-OR, 997-OR, A700-OR, or 996-GN
- General problem within the wiring harness (chafed insulation, pinched wire, etc.)
- Blown fuse in the lamp circuit
- Faulty ECM
- Intermittent connection issue
How to troubleshoot CAT Engine 2835: first checks
- Use the diagnostic scan tool's Override Parameters screen to command the lamp on and confirm whether the bulb itself lights up.
- Inspect the lamp bulb and its socket for damage, corrosion, or a burned-out element.
- Check the lamp circuit connectors (both at the lamp and along the harness) for corrosion, looseness, or physical damage.
- Trace wire 430-BU for chafing, pinches, or exposed conductor that could cause a short to ground or to power, paying attention to the specific wires it can short through (993-BR, 998-BR, 229-BK for ground shorts, 150-OR, 997-OR, A700-OR, 996-GN for power shorts).
- Check the digital return wire (998-BR) connection at the ECM and at the lamp for integrity.
- Check the fuse feeding the lamp circuit.
- If wiring, connectors, bulb, and fuse all check out, suspect the ECM itself.
How the code clears
No separate clearing step is listed beyond fixing the underlying wiring, bulb, fuse, or connector problem. Once the short or open condition in wire 430-BU is repaired and the lamp circuit reads correctly (the ECM sees enough current draw when it commands the lamp on), the code should stop being active. The event will remain logged in ECM memory as a historical fault unless cleared with the diagnostic scan tool.
Affected models and serial ranges
2835 appears in our records across 2 CAT Engine models. Match your machine by model and serial number.
| Model | Serial ranges |
|---|---|
| C11 | Serial range not listed in source records |
| C13 | Serial range not listed in source records |
Frequently asked questions
What does CAT code 2835 mean?
It means the engine ECM detected an open circuit or a short to battery positive in the Air Filter Restriction Lamp wiring, specifically wire 430-BU, after the ECM had been powered for at least 2 seconds. It is a lamp circuit problem, not confirmation of an actual clogged air filter.
Does code 2835 mean my air filter is clogged?
Not necessarily. The actual restriction detection logic compares Atmospheric and Turbo Compressor Inlet pressure sensor signals separately. Code 2835 is about the lamp's electrical circuit failing, which means the lamp may not illuminate even if a real restriction exists.
Will code 2835 cause an engine power derate?
No. The power derate logic (up to 20 percent, based on pressure differences of 6.5 kpa (26 in H2O) or more, with 2 percent derate per kpa (4 in H2O) above that) is tied to an actual detected air restriction, not to this lamp circuit fault.
How do I test the Air Filter Restriction Lamp bulb?
Use the Override Parameters screen on a diagnostic scan tool to command the lamp on manually. If the bulb does not light, check the bulb, socket, and wiring for damage before suspecting the ECM.
Which wires should I check for code 2835?
Focus on wire 430-BU, the lamp circuit wire. Check for shorts to ground through wires 993-BR, 998-BR, or 229-BK, and shorts to power through wires 150-OR, 997-OR, A700-OR, or 996-GN, depending on your harness version.
Is code 2835 an emergency?
It is not an immediate safety emergency since it does not derate the engine directly. However, since it disables a warning lamp, it should be diagnosed promptly so you are not caught off guard by an undetected air restriction later.
Can a blown fuse cause code 2835?
Yes, a blown fuse in the lamp circuit is listed as a possible cause, along with a bad bulb, damaged wiring or connectors, harness problems, and a faulty ECM.