OBD-II Diagnostic Trouble Code
P2336 — Cylinder 1 Above Knock Threshold
P2336 means the knock sensor system detected knock in cylinder 1 above the ECM's threshold, beyond what spark retard could control. It applies to gasoline or spark-ignited engines, including natural gas engines in some trucks.
Severity 3/5
Less common on commercial trucks
Service this week
Severity
Service this week
Cylinder 1 Above Knock Threshold
Code
P2336
Category
Powertrain
Subsystem
Ignition
Truck-relevant
Less common
What this means for truckers
Service within a few days. Performance is likely degraded. Continuing to drive without service risks additional component damage.
Before you replace parts — try this first
P2336 on the Ignition system is most often low-octane or poor-quality fuel — not a dead part. On commercial diesels especially, work these in order before spending money on parts:
- Confirm the symptoms. Match what your truck is doing to the Symptoms section below. If the code is set but the symptoms are not there, clear the code and re-test after a drive cycle — it may not return.
- Clean and dry the sensor connector. Water, road salt, or oil seeping into a connector is the #1 fake sensor failure. Disconnect, look for green corrosion or moisture, spray with electrical contact cleaner, dry, reseat. Many faults clear here for $0.
- Inspect the wiring harness. Trace the wire from the sensor toward the ECM — look for chafing against the engine block, melted insulation near the turbo or exhaust, or pinch points where a clamp has rubbed through.
- Test the sensor before swapping it. Most Common Causes (below) list the expected voltage or resistance range — a $20 multimeter saves a $300 sensor swap that does not fix the problem.
- Only then, replace the part. Use the OEM or a tier-1 aftermarket. Cheap sensors throw the same code in two weeks.
Symptoms
Audible pinging or knocking under load, reduced power from timing retard, and the check-engine light. Severe knock can damage pistons if ignored.
Common causes
- CommonLow-octane or poor-quality fuel ($0–$100)
- OccasionalCarbon buildup in the combustion chamber ($150–$600)
- OccasionalLean condition or overheating in cylinder 1 ($100–$800)
- OccasionalFaulty knock sensor or noisy mechanical component falsely detected as knock ($150–$500)
- RareWrong spark plug heat range ($80–$250)
How to fix
Fill with fuel of the specified octane and retest
When to use: First, especially after a recent fill-up
Check coolant temperature and cylinder 1 fuel trim
When to use: When knock continues on good fuel
Perform carbon cleaning
When to use: On high-mileage engines
Inspect knock sensor and mounting torque
When to use: When no actual knock is audible
Affects most
No specific vehicle pattern found in our complaint database. This code can appear on any vehicle that supports OBD-II diagnostics.
Related
- → Browse all DTC trouble codes
- → Decode a VIN to check codes for your truck
- → Owner-operator maintenance guides
- → P2300 — Ignition Coil A Primary Control Circuit Low
- → P2301 — Ignition Coil A Primary Control Circuit High
- → P234C — Turbocharger Boost Control A Performance
- → P234D — Turbocharger Boost Control A Low
- → P234E — Turbocharger Boost Control A High
Frequently Asked Questions
Can I drive with code P2336?
P2336 is severity 3 — plan service within a few days. Performance is likely degraded already (you may feel reduced power, harsher shifts, or slightly worse fuel economy). Continuing to drive risks additional damage to adjacent components.
How much does it cost to fix P2336 on a commercial truck?
Total repair cost ranges varies depending on the root cause. The cheapest fix is usually the first one listed below — Low-octane or poor-quality fuel — which is also the most common. On commercial trucks the cost is usually higher than passenger vehicles due to part availability and shop labor rates ($120–185/hour at most truck shops, vs $90–130 at general auto shops). DIY-capable fixes (sensors, hoses, filters) are at the low end; major component replacements (turbo actuator, high-pressure fuel pump, transmission solenoid pack) are at the high end. Always diagnose with a scan tool BEFORE replacing parts — guessing wrong on a $1,500 turbo actuator when the actual issue was a $30 boost hose is a common expensive mistake.
Will P2336 fail a DOT inspection?
P2336 is generally not a direct DOT inspection fail item by itself. Inspectors focus on safety-critical systems (brakes, steering, tires, lights, hours-of-service). However, the check engine light alone can trigger additional inspection scrutiny. Best practice: fix the code and clear it before a planned inspection.
What's the difference between P2336 and related codes?
P2336 is closely related to: P2300 (Ignition Coil A Primary Control Circuit Low), P2301 (Ignition Coil A Primary Control Circuit High), P234C (Turbocharger Boost Control A Performance), P234D (Turbocharger Boost Control A Low). These codes share the same subsystem (ignition) and often appear together. If you see this code, scan for the full code list — fixing the root cause usually clears multiple companion codes at once. If only P2336 is set without the companions, the issue is more isolated.
How do I prevent P2336 from coming back after a repair?
For P2336 (Cylinder 1 Above Knock Threshold), prevention centers on the ignition system. Use OEM-spec injectors and spark plugs (gas). Address fuel quality issues immediately — bad fuel kills injectors. Cylinder balance test annually for early warning.