Check Engine Light Chevy Silverado: Complete Codes & Fix Guide 2025

Is your check engine light on in your Chevy Silverado? You're not alone—and you're in the right place. Whether you're staring at a code reader showing P0300, wondering what P2135 means, or trying to decode a P349F message on your 2020 Silverado, this complete guide covers every common check engine light code specific to Chevrolet Silverado trucks from 2014-2025.

At Rohnert Park Transmission & Auto Repair, we've diagnosed thousands of Chevy Silverado check engine light issues over our 28+ years serving Sonoma County. We've compiled our real-world OBD-II diagnostic experience into this comprehensive reference, organized by code type with urgency levels, common causes, and repair cost estimates. **Bookmark this page**—you'll want it next time that amber light appears.

What Does Check Engine Light Mean on Chevy Silverado?

When your Chevy Silverado's check engine light (also called the Malfunction Indicator Lamp or MIL) illuminates, it means your truck's onboard computer has detected a problem in the emissions, engine, or powertrain systems. The computer stores a diagnostic trouble code (DTC) that pinpoints what triggered the warning.

Solid check engine light: Indicates a non-emergency issue that should be diagnosed soon. You can typically drive to a shop, but don't ignore it for weeks.

Flashing/blinking check engine light: This is urgent—it indicates active engine misfires that can damage your catalytic converter. [Pull over safely and don't drive until diagnosed](/blog/chevy-silverado-check-engine-light-flashing-then-stops).

Silverados are particularly prone to check engine lights due to their Active Fuel Management (AFM) and Dynamic Fuel Management (DFM) systems, which can trigger codes when lifters or solenoids begin failing. Understanding what your specific code means is the first step to getting it fixed properly.

Quick Reference: How Urgent Is Your Code?

Before diving into specific codes, understand the urgency system we use throughout this guide:

| Urgency | What It Means | Action Required |

|---------|---------------|-----------------|

| 🔴 **STOP** | Active damage occurring | Pull over safely, don't drive |

| 🟡 **SOON** | Needs attention within days | Schedule diagnosis this week |

| 🟢 **MONITOR** | Not immediately dangerous | Diagnose when convenient |

Important: A flashing check engine light ALWAYS means stop driving immediately, regardless of code. [Learn more about flashing vs solid CEL](/blog/check-engine-light-flashing-vs-solid).

Understanding Chevy Silverado Check Engine Codes

How to Read Your Silverado OBD-II Code

Every Silverado from 1996 onward uses the OBD-II diagnostic system. Your diagnostic trouble code (DTC) follows this format:

```

P 0 3 0 0

│ │ │ └─ Specific fault number

│ │ └─── Sub-system (0-9)

│ └───── Code type (0=Generic, 1=Manufacturer)

└─────── System (P=Powertrain, B=Body, C=Chassis, U=Network)

```

Silverado-specific codes often start with P1xxx or P3xxx—these are GM manufacturer codes that generic code readers may not fully interpret.

Where to Find Your OBD-II Port

Your Silverado's diagnostic port (DLC) is located under the dashboard on the driver's side, usually to the left of the steering column. On 2019+ models, it may be behind a small cover panel.

Generic vs. Professional Scanners

Basic OBD-II readers show generic codes but miss:

• GM-specific codes (P1xxx, P2xxx manufacturer codes)

• AFM/DFM system status

• Freeze frame data showing conditions when code set

• Pending codes not yet confirmed

Professional GM diagnostic tools reveal the complete picture, which is why we recommend professional diagnosis for persistent or multiple codes.

Year-Specific Code Differences

2014-2019 Silverado Check Engine Codes (K2XX Platform)

These trucks use **Active Fuel Management (AFM)**, which deactivates cylinders 1, 4, 6, and 7 under light load. AFM-related check engine codes are extremely common:

• **AFM lifter failures** trigger misfire codes on cylinders 1, 4, 6, 7

• **P1174** (Fuel Trim Cylinder Balance) indicates AFM imbalance

• Oil consumption issues often accompany AFM codes

• GM TSB 18-NA-355 addresses many AFM-related faults

Model-specific issues:

• 2014-2015: Early 8L90 transmission integration problems

• 2016-2017: Peak AFM lifter failure rates

• 2018-2019: Improved but still AFM-susceptible

2019-2025 Silverado Check Engine Codes (T1XX Platform)

These trucks use **Dynamic Fuel Management (DFM)**, which can run on any cylinder combination (not just 4 or 8). New check engine code patterns include:

• **P349X series** codes for cylinder deactivation faults

• **P3400/P3401** for bank-specific deactivation issues

• Software-related codes requiring TCM updates

• More sophisticated sensor codes

Model-specific issues:

• 2019-2020: DFM calibration issues, TSB 21-NA-152

• 2021-2022: Cold start engagement problems, TSB 22-NA-089

• 2023-2025: Generally improved, fewer DFM complaints

---

Engine Misfire Codes

Misfire codes are among the most common—and most urgent—Silverado check engine light codes.

P0300 - Random/Multiple Cylinder Misfire 🔴

What it means: Multiple cylinders are misfiring without a consistent pattern.

Silverado-specific causes:

• Failing AFM lifters (2014-2019)

• DFM transition problems (2019-2024)

• Worn spark plugs (especially at 100,000+ miles)

• Ignition coil failures (common on cylinders 1, 4, 6, 7)

• Vacuum leaks at intake manifold

• Fuel injector problems

Urgency: 🔴 STOP if flashing, 🟡 SOON if solid

Why it matters: Unburned fuel damages your catalytic converter. Each misfire event can cost hundreds in converter damage.

Repair cost: Varies depending on cause—call (707) 584-7727 for an accurate estimate

P0301-P0308 - Cylinder-Specific Misfire Codes 🔴

These codes identify exactly which cylinder is misfiring:

| Code | Cylinder | Common Silverado Cause |

|------|----------|------------------------|

| P0301 | Cylinder 1 | AFM lifter, spark plug, coil |

| P0302 | Cylinder 2 | Spark plug, coil, injector |

| P0303 | Cylinder 3 | Spark plug, coil, injector |

| P0304 | Cylinder 4 | **AFM lifter failure (very common)** |

| P0305 | Cylinder 5 | Spark plug, coil, injector |

| P0306 | Cylinder 6 | **AFM lifter failure (very common)** |

| P0307 | Cylinder 7 | **AFM lifter failure (very common)** |

| P0308 | Cylinder 8 | Spark plug, coil, DFM solenoid |

Key insight: Repeated misfires on cylinders 1, 4, 6, or 7 strongly indicate AFM component failure. These are the cylinders that deactivate under AFM operation.

Urgency: 🔴 STOP if flashing, 🟡 SOON if solid

Repair cost: Varies by component—contact us for a specific quote

P0316 - Engine Misfire on Startup 🟡

What it means: Misfires occurring within the first 1,000 engine revolutions after cold start.

Silverado-specific causes:

• Leaking fuel injectors (fuel seeps overnight)

• Weak ignition coil that fails when cold

• Carbon buildup on intake valves (direct injection models)

• Cold weather affecting AFM lifter operation

Urgency: 🟡 SOON - Schedule diagnosis within a week

Repair cost: Contact us for an estimate based on your specific situation

---

AFM/DFM Cylinder Deactivation Codes

These codes are **unique to Silverado V8 engines** with cylinder deactivation systems.

P3400 - Cylinder Deactivation System Bank 1 🟡

What it means: The cylinder deactivation system on Bank 1 (cylinders 1, 3, 5, 7) is malfunctioning.

Common causes:

• AFM/DFM solenoid failure

• Low oil pressure affecting lifter operation

• Wiring harness damage to lifter solenoids

• ECM calibration issues

Urgency: 🟡 SOON - Can cause rough running and misfire codes

P3401 - Cylinder Deactivation System Bank 2 🟡

What it means: Same as P3400 but for Bank 2 (cylinders 2, 4, 6, 8).

Repair cost for P3400/P3401: Varies—call for a quote

P349F - Cylinder 8 Deactivation Fault 🟡

What it means: Cylinder 8's deactivation solenoid or lifter is not responding correctly.

Why it's common: On 2019-2024 Silverados with DFM, this code frequently appears due to:

• Software bugs in early production years

• Solenoid calibration issues

• Oil viscosity problems affecting hydraulic lifter response

Urgency: 🟡 SOON - Often resolved with software update

GM TSB Reference: TSB 21-NA-152 addresses this issue

P1174 - Fuel Trim Cylinder Balance (AFM Related) 🟡

What it means: The engine computer detected a fuel trim imbalance between AFM and non-AFM cylinders.

Silverado-specific insight: This code often precedes more serious AFM failures. If you see P1174, monitor closely for developing misfire codes.

Urgency: 🟡 SOON - Early warning of potential AFM failure

Repair cost: Varies from minor software updates to major component replacement—contact us for diagnosis

---

Throttle & Sensor Codes

These codes relate to the electronic throttle control system—extremely common on Silverados.

P0120 - Throttle Position Sensor Circuit Malfunction 🟡

What it means: The throttle position sensor is sending incorrect or erratic signals.

Silverado symptoms:

• "Reduced Engine Power" message

• Erratic idle

• Hesitation during acceleration

• Limp mode (limited to ~20-30 mph)

Common causes:

• Dirty throttle body

• Failed TPS sensor

• Wiring harness damage (common at firewall connector)

• Corroded ground connections

Urgency: 🟡 SOON - May trigger limp mode unexpectedly

Related guide: [Reduced Engine Power Chevy Silverado](/blog/reduced-engine-power-chevy-silverado-complete-guide)

P0122 - Throttle Position Sensor Low Input 🟡

What it means: The TPS signal is reading below expected minimum voltage.

Silverado-specific: Often caused by corroded connector pins or damaged wiring at the firewall pass-through—a known weak point on 2007-2019 models.

Urgency: 🟡 SOON

Repair cost: Call for an estimate

P2135 - Throttle/Pedal Position Correlation 🔴

What it means: The throttle body position and accelerator pedal position sensors disagree with each other.

Why it's serious: This code typically triggers immediate "Reduced Engine Power" mode. Your truck may become undriveable.

Silverado causes:

• Failed throttle body assembly

• Accelerator pedal position sensor failure

• Wiring short between TPS and APP sensors

• Ground circuit problems

Urgency: 🔴 STOP if in limp mode, 🟡 SOON otherwise

Repair cost: Varies by component—contact us for diagnosis and quote

P0101 - MAF Sensor Performance 🟢

What it means: The Mass Air Flow sensor is reading outside expected parameters.

Silverado causes:

• Dirty MAF sensor element (most common)

• Air filter restriction

• Intake air leak after MAF sensor

• Failed MAF sensor

DIY fix: Clean MAF sensor with dedicated MAF cleaner spray (NOT carburetor cleaner)

Urgency: 🟢 MONITOR - Safe to drive, may affect fuel economy

Repair cost: Cleaning is affordable; replacement costs vary—call for quote

---

Fuel System Codes

P0171 - System Too Lean (Bank 1) 🟡

What it means: The engine is getting too much air or not enough fuel on Bank 1.

Silverado-specific causes:

• Intake manifold gasket leak (very common on 5.3L)

• PCV valve failure

• Vacuum line cracks

• Weak fuel pump

• Dirty fuel injectors

Urgency: 🟡 SOON - Prolonged lean operation damages engine

P0174 - System Too Lean (Bank 2) 🟡

Same as P0171 but affecting Bank 2. **If both P0171 and P0174 appear together**, suspect:

• Failing fuel pump

• Clogged fuel filter

• Major vacuum leak

• MAF sensor issues

Repair cost: Varies by cause—contact us for diagnosis

P0172 - System Too Rich (Bank 1) 🟡

What it means: The engine is getting too much fuel or not enough air.

Silverado causes:

• Leaking fuel injector

• Failed oxygen sensor giving false lean reading

• Clogged air filter

• High fuel pressure

Urgency: 🟡 SOON - Wastes fuel and can damage catalytic converter

P0175 - System Too Rich (Bank 2) 🟡

Same as P0172 for Bank 2.

Repair cost: Depends on root cause—call for estimate

---

EVAP System Codes

These codes relate to the evaporative emission control system that prevents fuel vapors from escaping.

P0442 - EVAP Small Leak Detected 🟢

What it means: A small leak in the fuel vapor system.

Most common cause: Loose or worn gas cap. Try this first: Remove gas cap, inspect seal, reinstall and tighten until it clicks 3 times.

Other causes:

• Cracked EVAP hose

• Failed purge valve

• Charcoal canister damage

Urgency: 🟢 MONITOR - No immediate danger, may fail emissions test

P0455 - EVAP Large Leak Detected 🟡

What it means: A significant leak in the fuel vapor system.

Check immediately: Is your gas cap missing or very loose?

If cap is secure:

• Disconnected vapor line

• Failed vent valve

• Cracked fuel tank or filler neck

Urgency: 🟡 SOON - May smell fuel, potential fuel loss

P0446 - EVAP Vent Control Circuit 🟢

What it means: The vent valve that allows the EVAP system to breathe isn't working correctly.

Silverado-specific: The vent valve is located near the charcoal canister under the truck. Mud, debris, or spider webs can block it.

Urgency: 🟢 MONITOR

EVAP repair cost: Varies by component—call for quote

---

Emissions Codes

P0420 - Catalyst Efficiency Below Threshold (Bank 1) 🟡

What it means: Your catalytic converter isn't cleaning exhaust gases effectively.

Before replacing the converter, check:

• Oxygen sensor accuracy (front and rear)

• Exhaust leaks before the converter

• Recent engine misfires (which damage converters)

Silverado note: California CARB-compliant converters cost significantly more than federal-spec units.

Urgency: 🟡 SOON - Will fail smog test

Related guide: [P0420 Code Complete Guide](/blog/p0420-code-catalytic-converter-guide)

P0430 - Catalyst Efficiency Below Threshold (Bank 2) 🟡

Same as P0420 for Bank 2 (V8 engines have two converters).

Repair cost: Catalytic converter replacement varies by type and vehicle—call for quote

P0401 - EGR Insufficient Flow 🟢

What it means: The Exhaust Gas Recirculation system isn't flowing enough exhaust back into the intake.

Silverado causes:

• Carbon buildup in EGR passages

• Failed EGR valve

• Clogged EGR cooler

Urgency: 🟢 MONITOR - May cause slight ping under load

Repair cost: Contact us for an accurate estimate

---

Transmission-Related CEL Codes

While these are technically transmission codes, they trigger the check engine light on Silverados.

P0700 - Transmission Control System Malfunction 🔴

What it means: The transmission computer detected a fault and stored additional codes.

Critical: P0700 is an "informational" code—there are ALWAYS additional codes stored. A professional scan will reveal the specific transmission issue.

Common accompanying codes:

• P0751-P0756 (shift solenoid faults)

• P0717 (input speed sensor)

• P0722 (output speed sensor)

Urgency: 🔴 STOP if transmission is slipping or not shifting

Related guide: [Silverado Transmission Repair Guide](/vehicles/chevrolet/silverado/repair-guide)

P1870 - Transmission Component Slipping 🔴

What it means: Internal transmission slippage detected, typically the torque converter clutch.

Silverado-specific: This code is common on trucks with the 4L60E/4L65E (older) and 8L90 (2015+) transmissions. The infamous 8L90 shudder often triggers this code.

Urgency: 🔴 STOP - Continued driving causes rapid transmission damage

Repair cost: Transmission repairs vary significantly—call for diagnosis and quote

P0751-P0756 - Shift Solenoid Codes 🟡

What they mean: Electrical or performance faults in specific shift solenoids.

| Code | Solenoid | Affects |

|------|----------|---------|

| P0751 | Shift Solenoid A | 1-2 shift |

| P0752 | Shift Solenoid A Stuck | 1-2 shift |

| P0753 | Shift Solenoid A Electrical | 1-2 shift |

| P0756 | Shift Solenoid B | 2-3 shift |

Urgency: 🟡 SOON - May cause harsh or delayed shifts

Repair cost: Call for solenoid repair estimate

---

Oxygen Sensor Codes

P0131 - O2 Sensor Low Voltage (Bank 1 Sensor 1) 🟡

What it means: The upstream oxygen sensor on Bank 1 is reading lower voltage than expected.

Causes:

• Failed oxygen sensor

• Exhaust leak before sensor

• Wiring issues

Urgency: 🟡 SOON - Affects fuel mixture and economy

P0134 - O2 Sensor No Activity (Bank 1 Sensor 1) 🟡

What it means: The oxygen sensor isn't switching between rich and lean as expected.

Most common cause: Failed oxygen sensor. On high-mileage Silverados, O2 sensors typically need replacement every 100,000-150,000 miles.

Urgency: 🟡 SOON

P0137/P0138 - O2 Sensor (Bank 1 Sensor 2) 🟢

What they mean: Issues with the downstream (post-catalytic converter) oxygen sensor.

Note: Downstream sensor codes often accompany P0420/P0430 converter codes. Replace sensors first before condemning the converter.

O2 sensor repair cost: Varies per sensor—call for quote

---

Cooling System Codes

P0128 - Coolant Temperature Below Thermostat Range 🟢

What it means: The engine isn't reaching normal operating temperature.

Most common cause: Stuck-open thermostat

Symptoms:

• Temperature gauge stays low

• Poor heater performance

• Reduced fuel economy

Urgency: 🟢 MONITOR - Not dangerous but wastes fuel

Repair cost: Call for thermostat replacement estimate

P0117/P0118 - Coolant Temperature Sensor 🟡

What they mean: The coolant temperature sensor is reading too low (P0117) or too high (P0118).

Urgency: 🟡 SOON - Affects fuel mixture and can trigger other issues

Repair cost: Contact us for sensor replacement quote

---

How to Read Codes Without a Scanner

On some 2019+ Silverados, you can view basic codes through the Driver Information Center:

1. Turn ignition to "On" (don't start engine)

2. Press and hold the odometer reset button

3. Turn ignition to "Off" then back to "On" while holding button

4. If available, codes will display on DIC

Limitation: This method only shows codes on certain trim levels and doesn't provide freeze frame data or pending codes. We recommend using a proper OBD-II scanner or visiting a shop for accurate diagnosis.

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When DIY Diagnosis Isn't Enough

While basic code readers help, you need professional diagnosis when:

• **Multiple codes appear** - Need to identify root cause vs. symptoms

• **Codes return after clearing** - Underlying problem persists

• **Intermittent codes** - Freeze frame data needed to catch the fault

• **AFM/DFM codes present** - GM-specific equipment required

• **Transmission codes appear** - Complex diagnostics needed

• **"Reduced Engine Power" triggered** - Multiple systems may be involved

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Get an Accurate Repair Quote

Repair costs vary significantly based on your specific vehicle, the root cause, and parts required. Rather than guess based on general estimates, **call (707) 584-7727** for an accurate quote on your specific Silverado. We provide transparent pricing with no hidden fees.

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Frequently Asked Questions

Can I drive my Silverado with the check engine light on?

If the light is solid: Usually safe for short distances if the engine runs smoothly. However, continued driving with certain codes (especially misfire codes) can cause expensive catalytic converter damage. Get it diagnosed within a few days.

If the light is flashing: Stop driving immediately. A flashing CEL indicates active misfires severe enough to damage the converter. Pull over safely and have the truck towed.

Why does my Silverado check engine light come on then go off?

This indicates an intermittent fault. The computer detected a problem, but conditions returned to normal. The code is stored as a "pending code" and will become a confirmed code if the fault repeats. Get it scanned—the stored code reveals what happened.

How do I reset the check engine light on my Silverado?

You can clear codes with an OBD-II scanner or by disconnecting the battery for 15 minutes. However, **clearing codes doesn't fix the problem**—if the underlying issue remains, the light will return. Only clear codes after repairs are complete.

What's the most common check engine code on Silverados?

Based on our experience, **P0300 (random misfire)** is the most common, followed by P2135 (throttle position correlation) and various AFM-related codes (P1174, P0300-series on cylinders 1, 4, 6, 7).

Why do Silverados have so many AFM problems?

Active Fuel Management saves fuel by deactivating 4 cylinders under light load, but it creates additional stress on lifters and valves. The constant on/off cycling accelerates wear. Many owners opt for AFM delete kits or disablers to prevent these issues.

Should I get an AFM disabler for my Silverado?

If you're experiencing AFM-related misfires (P0300 on cylinders 1, 4, 6, 7) or want to prevent them, an AFM disabler can help. Options include the Range AFM Disabler (plug-and-play) or ECM tuning (permanent). Trade-off: slightly reduced fuel economy for improved reliability.

Are P0171/P0174 codes serious on a Silverado?

These lean codes indicate the engine isn't getting enough fuel relative to air. While you can drive short distances, prolonged lean operation causes engine damage. Most commonly caused by vacuum leaks at the intake manifold—a known issue on 5.3L engines.

What does P0700 mean on my Silverado?

P0700 is an informational code indicating the transmission computer detected a fault. It's always accompanied by more specific transmission codes. A professional scan tool is required to read the full transmission fault codes and determine the actual problem.

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Get Expert Silverado Diagnosis in Rohnert Park

Whether your check engine light just came on or you've been chasing intermittent codes for months, we can help. **Rohnert Park Transmission & Auto Repair** specializes in Chevrolet Silverado diagnostics and repair:

• ✅ **GM-specific diagnostic equipment** reads all codes including manufacturer-specific

• ✅ **ASE & ATRA certified technicians** with Silverado expertise

• ✅ **28+ years serving Sonoma County** drivers

• ✅ **AFM/DFM system specialists** - we've seen every variation

• ✅ **BBB A+ rated** with 4.8-star reviews

• ✅ **Transparent pricing** with written estimates before any work

Call us at (707) 584-7727 or [schedule online](/contact) for professional check engine light diagnosis. We'll read your codes, explain exactly what they mean for YOUR truck, and provide honest repair recommendations.

Located at **305 Laguna Drive in Rohnert Park**, we serve Silverado owners throughout Sonoma County including Santa Rosa, Petaluma, Cotati, Sebastopol, Windsor, and Novato.

Don't guess at check engine codes. Get the complete picture from technicians who specialize in Silverado diagnostics.