Injector Cylinder 5 Circuit
The PACCAR-P1026 (PACCAR MX) diesel fault code means: Injector Cylinder 5 Circuit. This is a serious severity code.
- Keep driving?
- Short distances only
- DIY difficulty
- intermediate
- Estimated cost
- $400-$3,500
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View pilot availability →What Are the Symptoms of PACCAR-P1026?
- Power loss / derate
- Rough idle or misfire
- Hard starting or no-start
- Excessive smoke or fuel smell
- Check Engine Light illuminated
What Causes PACCAR-P1026? (Most Likely First)
- Failed injector or pressure sensor Likely
- Wiring harness damage at injector/sensor connector Likely
- Contaminated fuel or plugged filter Possible
- CP3 pump wear (high mileage) Possible
- Fuel rail pressure relief valve stuck Less Likely
Can I Still Drive with PACCAR-P1026?
Short distances only. PACCAR-P1026 is rated serious severity. Keep trips short and get it diagnosed soon rather than waiting for symptoms to worsen.
Frequently Asked Questions
What does PACCAR MX code P1026 mean?
PACCAR MX code P1026 (Injector Cylinder 5 Circuit) is a serious-severity diagnostic trouble code set by the engine or aftertreatment control module on MX-11 and MX-13 engines in Kenworth and Peterbilt trucks. It indicates a fault in the fuel system that should be diagnosed with DAVIE4 or PACCAR ESA.
Can I drive a Kenworth or Peterbilt with PACCAR P1026?
Possibly — short distances may be OK, but ignoring the fault risks progressive damage, regen failure, or derate. Address promptly.
How much does it cost to fix PACCAR MX P1026?
Typical repair runs $400-$3,500. Sensor or wiring repairs are at the low end; injector, DEF pump, DPF, or EGR cooler jobs are at the high end. Dealer-level DAVIE4 software is often required for programming or calibration after parts replacement.
Mechanics Guide Step-by-step diagnosis
How Do You Diagnose PACCAR-P1026?
Connect DAVIE4 and capture fuel rail pressure actual vs commanded during idle and snap-accel.
Inspect fuel filter(s) and water separator — replace if service interval exceeded.
Check injector wiring harness for chafing near valve cover and connector seal integrity.
Run injector balance / cut-out test with DAVIE4 to identify weak cylinder.
If CP3 pump is suspected, measure return-line flow and replace pump if excessive leakback.
Sources 1
This page is built from documented references. Verify against your own service info before repair work.
- SAE J1939-73Application Layer: Diagnostics (defines the SPN/FMI fault-identifier framework)
P1026 on Other Platforms
The same code ID appears across other engines, vehicles, and equipment. Diagnostic flow varies by platform — see the matching breakdown:
Which Vehicles Commonly Get PACCAR-P1026?
- Kenworth T680 with PACCAR MX-13
- Kenworth T880 with PACCAR MX-13
- Kenworth W990 with PACCAR MX-13
- Peterbilt 579 with PACCAR MX-13
- Peterbilt 389 with PACCAR MX-13
- Peterbilt 567 with PACCAR MX-13
- Kenworth T440 with PACCAR MX-11
- Kenworth T470 with PACCAR MX-11
- Peterbilt 520 with PACCAR MX-11
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