Reductant Injector Circuit High
The PACCAR-P2049 (PACCAR MX) diesel fault code means: Reductant Injector Circuit High. This is a serious severity code.
- Keep driving?
- Short distances only
- DIY difficulty
- intermediate
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What Are the Symptoms of PACCAR-P2049?
- Check Engine light
- DEF dosing stops, which can lead to an emissions warning and, if left, a derate
What Causes PACCAR-P2049? (Most Likely First)
- Injector circuit shorted to voltage High
- Failed DEF injector Medium
- Damaged connector Medium
Can I Still Drive with PACCAR-P2049?
Short distances only. PACCAR-P2049 is rated serious severity. Keep trips short and get it diagnosed soon rather than waiting for symptoms to worsen.
Frequently Asked Questions
What does P2049 mean on a PACCAR MX?
P2049 means Reductant Injector Circuit High. The control module detected high voltage in the bank 1 unit 1 reductant (DEF) injector circuit.
Is P2049 a PACCAR MX-specific code?
No. P2049 is a generic OBD-II code defined by SAE J2012, so it means the same thing on any vehicle that sets it. The exact conditions PACCAR uses to set it on its diesels are in PACCAR service information.
Mechanics Guide Step-by-step diagnosis
How Do You Diagnose PACCAR-P2049?
Check the circuit for a short to voltage with the injector unplugged.
Check the injector coil resistance.
Inspect the connector and harness.
Sources 3
This page is built from documented references. Verify against your own service info before repair work.
- California Code of Regulations, Title 13 section 1971.1 (Heavy-Duty OBD)malfunction criteria, section (e)
- SAE J1939-73Application Layer: Diagnostics (defines the SPN/FMI fault-identifier framework)
- SAE J2012Diagnostic Trouble Code Definitions (defines P2049 as a generic OBD-II code)
P2049 on Other Platforms
The same code ID appears across other engines, vehicles, and equipment. Diagnostic flow varies by platform — see the matching breakdown:
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