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GMC • 2020–2026Near-Luxury

GMC Sierra 1500 OBD-II Diagnostic Guide

Comprehensive diagnostic trouble code telemetry, sensor voltage thresholds, and step-by-step repair manuals for GMC Sierra 1500 models equipped with 5.3L / 6.2L EcoTec3 V8 (Denali 420HP) / 3.0L Duramax Turbo-Diesel.

DLC OBD-II Port: Under driver dashboard, left of steering column
GMC Sierra 1500 (2020–2026)2020–2026Truck
DLC Port:SAE J1962 (16-Pin)
Bus Protocol:500 kbps CAN-FD
Operating Voltage:12.0V – 14.4V Nom.
Engine Powertrain
5.3L / 6.2L EcoTec3 V8 (Denali 420HP) / 3.0L Duramax Turbo-Diesel
Factory Tolerances
Diagnostic Gateway
16-Pin SAE J1962
Driver Footwell DLC
Sensor Signal Tolerance
5.0V Ref (±0.1V)
OEM Direct Telemetry
Diagnostic Protocol
SAE J1979 / ISO 15765
Mode $01–$0A Verified
Other GMC Vehicle Models:
GMC Sierra 1500GMC Yukon
NHTSA VERIFIED DEFECT TELEMETRY2014–2025 Model Years

GMC Sierra 1500 Problem & Reliability Intelligence by Year

Explore Multi-Year Audit
Model-Specific Telemetry

Top Check Engine Trouble Codes for GMC Sierra 1500

P0300Sierra 1500 Specific
Est. DIY Parts: $100 - $600 (DIY: $30 - $120)

P0300 on GMC Sierra 1500: Diagnosis & Fix

Troubleshooting procedure for P0300: P0300: Random or Multiple Cylinder Misfire Detected specifically affecting GMC Sierra 1500 (5.3L / 6.2L EcoTec3 V8 (Denali 420HP) / 3.0L Duramax Turbo-Diesel).

5-Step DIY GuideFix Sierra 1500
P0420Sierra 1500 Specific
Est. DIY Parts: $400 - $1,800 (DIY: $150 - $400)

P0420 on GMC Sierra 1500: Diagnosis & Fix

Troubleshooting procedure for P0420: P0420: Catalyst System Efficiency Below Threshold (Bank 1) specifically affecting GMC Sierra 1500 (5.3L / 6.2L EcoTec3 V8 (Denali 420HP) / 3.0L Duramax Turbo-Diesel).

5-Step DIY GuideFix Sierra 1500
P0171Sierra 1500 Specific
Est. DIY Parts: $80 - $350 (DIY: $15 - $70)

P0171 on GMC Sierra 1500: Diagnosis & Fix

Troubleshooting procedure for P0171: P0171: System Too Lean (Bank 1) specifically affecting GMC Sierra 1500 (5.3L / 6.2L EcoTec3 V8 (Denali 420HP) / 3.0L Duramax Turbo-Diesel).

5-Step DIY GuideFix Sierra 1500
P0520Sierra 1500 Specific
Est. DIY Parts: $130 - $320 (DIY: $25 - $60)

P0520 on GMC Sierra 1500: Diagnosis & Fix

Troubleshooting procedure for P0520: P0520: Engine Oil Pressure Sensor/Switch Circuit Malfunction specifically affecting GMC Sierra 1500 (5.3L / 6.2L EcoTec3 V8 (Denali 420HP) / 3.0L Duramax Turbo-Diesel).

5-Step DIY GuideFix Sierra 1500
Full Diagnostic Library

All OBD-II Codes for GMC Sierra 1500

Showing 1–18 of 122 codes
Active:
1. Filter by Vehicle Manufacturer (25 Makes)
2. DTC System Category
3. Risk Severity Level
P0300Critical Severity
Est. DIY: $100 - $600 (DIY: $30 - $120)

P0300: Random or Multiple Cylinder Misfire Detected

Flashing Check Engine Light (CEL) • Engine shaking, vibrating, or jerking at idle

5 Step DIY GuideTroubleshoot
P0420Medium Severity
Est. DIY: $400 - $1,800 (DIY: $150 - $400)

P0420: Catalyst System Efficiency Below Threshold (Bank 1)

Illuminated Check Engine Light (steady) • Rotten egg / sulfur odor from exhaust

5 Step DIY GuideTroubleshoot
P0171Medium Severity
Est. DIY: $80 - $350 (DIY: $15 - $70)

P0171: System Too Lean (Bank 1)

Check Engine Light on • Rough idling or engine hesitation on acceleration

5 Step DIY GuideTroubleshoot
P0128Low Severity
Est. DIY: $120 - $300 (DIY: $25 - $60)

P0128: Coolant Temperature Below Thermostat Regulating Temperature

Check Engine Light • Cabin heater takes too long to warm up

5 Step DIY GuideTroubleshoot
P0455Low Severity
Est. DIY: $15 - $250 (DIY: $15 - $50)

P0455: Evaporative Emission Control System Leak Detected (Gross Leak)

Check Engine Light on • Gas cap loose warning message on dashboard

5 Step DIY GuideTroubleshoot
P0101Medium Severity
Est. DIY: $45 - $220 (DIY Clean: $12)

Mass Air Flow (MAF) Sensor Circuit Range/Performance

Check Engine Light (CEL) illuminated • Rough or erratic engine idle

4 Step DIY GuideTroubleshoot
P0135Low to Medium Severity
Est. DIY: $80 - $240 (DIY Sensor: $45)

O2 Sensor Heater Circuit Malfunction (Bank 1, Sensor 1)

Check Engine Light on • Slightly increased fuel consumption on short trips

3 Step DIY GuideTroubleshoot
P0172Medium Severity
Est. DIY: $30 - $280 (DIY Clean: $15)

System Too Rich (Bank 1) - Symptoms, Causes & Step-by-Step Fix

Check Engine Light on • Strong unburnt fuel odor from exhaust

3 Step DIY GuideTroubleshoot
P0442Low Severity
Est. DIY: $25 - $200 (DIY: $15)

EVAP System Small Leak Detected - Diagnosis & Repair Guide

Check Engine Light on • Intermittent faint fuel odor near rear wheel well

3 Step DIY GuideTroubleshoot
P0507Medium Severity
Est. DIY: $40 - $250 (DIY Throttle Relearn: $0)

Idle Control System RPM Higher Than Expected - Diagnosis

Engine idles at 1,000+ RPM in park/neutral • RPM surges or hunts at red lights

3 Step DIY GuideTroubleshoot
P0010Moderate Severity
Est. DIY: $120 - $350 (DIY: $40 - $80)

P0010: Camshaft Position Actuator Circuit / Open (Bank 1)

System alert or indicator light illuminated (P0010) • Intermittent performance throttling or unexpected operation halts

5 Step DIY GuideTroubleshoot
P0011High Severity
Est. DIY: $150 - $450 (DIY: $50 - $120)

P0011: Camshaft Position - Timing Over-Advanced or System Performance (Bank 1)

System alert or indicator light illuminated (P0011) • Intermittent performance throttling or unexpected operation halts

5 Step DIY GuideTroubleshoot
P0012High Severity
Est. DIY: $150 - $450 (DIY: $50 - $120)

P0012: Camshaft Position - Timing Over-Retarded (Bank 1)

System alert or indicator light illuminated (P0012) • Intermittent performance throttling or unexpected operation halts

5 Step DIY GuideTroubleshoot
P0013Moderate Severity
Est. DIY: $120 - $320 (DIY: $40 - $75)

P0013: Exhaust Camshaft Position Actuator Circuit / Open (Bank 1)

System alert or indicator light illuminated (P0013) • Intermittent performance throttling or unexpected operation halts

5 Step DIY GuideTroubleshoot
P0014High Severity
Est. DIY: $150 - $420 (DIY: $45 - $90)

P0014: Exhaust Camshaft Position Timing Over-Advanced (Bank 1)

System alert or indicator light illuminated (P0014) • Intermittent performance throttling or unexpected operation halts

5 Step DIY GuideTroubleshoot
P0016Critical Severity
Est. DIY: $300 - $1,200 (DIY: $80 - $250)

P0016: Crankshaft Position - Camshaft Position Correlation (Bank 1 Sensor A)

System alert or indicator light illuminated (P0016) • Intermittent performance throttling or unexpected operation halts

5 Step DIY GuideTroubleshoot
P0017Critical Severity
Est. DIY: $300 - $1,200 (DIY: $80 - $250)

P0017: Crankshaft Position - Camshaft Position Correlation (Bank 1 Sensor B)

System alert or indicator light illuminated (P0017) • Intermittent performance throttling or unexpected operation halts

5 Step DIY GuideTroubleshoot
P0100Moderate Severity
Est. DIY: $100 - $300 (DIY: $15 - $80)

P0100: Mass or Volume Air Flow Circuit Malfunction

System alert or indicator light illuminated (P0100) • Intermittent performance throttling or unexpected operation halts

5 Step DIY GuideTroubleshoot
Technical FAQ

Frequently Asked Questions

Where is the OBD-II diagnostic port located on the GMC Sierra 1500?

On the GMC Sierra 1500 (2020–2026), the standard 16-pin DLC port is located: Under driver dashboard, left of steering column. It supports SAE J1979 / ISO 15765-4 CAN protocols for all handheld OBD-II code readers.

What are the most common Check Engine fault codes on the GMC Sierra 1500?

The most frequently logged trouble codes on the GMC Sierra 1500 (5.3L / 6.2L EcoTec3 V8 (Denali 420HP) / 3.0L Duramax Turbo-Diesel) include P0300, P0420, P0171, P0520.

How does an onboard diagnostic scan communicate with the GMC Sierra 1500?

Connecting an OBD-II scanner to the GMC Sierra 1500's 16-pin DLC port establishes a high-speed CAN link (ISO 15765-4) with the ECM/PCM. It interrogates SAE J1979 Modes $01 through $0A for active DTCs, freeze-frame sensor telemetry, and oxygen sensor readiness monitors.