P3402 GMC Diagnostic Trouble Code
Detailed technical diagnosis, symptoms, common causes, inspection procedures, and estimated repair costs.
⚠️ Can I Drive With Code P3402?
Safe to drive to a repair shop or home, but arrange inspection soon to maintain optimal efficiency and pass emissions.
🚨 Symptoms of Code P3402
- Check Engine Light (CEL / MIL) illuminated on dashboard
- Vehicle stored diagnostic trouble code in PCM memory
- Possible reduction in engine performance or fuel economy
- System operating under fail-safe or default backup parameters
🔍 Most Common Causes for Code P3402
- Faulty or degraded sensor related to auxiliary emission controls
- Damaged, corroded, or loose wiring harness connector
- Intermittent short circuit or open circuit to ground / reference voltage
- Software update required or internal controller calibration fault
🛠️ Step-by-Step Diagnostic & Multimeter Inspection Procedure
- Connect an OBD-II / EOBD scan tool and verify active and pending P3402 codes
- Inspect wiring harness and connector pins for corrosion, bent pins, or thermal damage
- Check circuit power and ground with a digital multimeter (DVOM)
- Review manufacturer Technical Service Bulletins (TSBs) for known vehicle issues
Common Diagnostic Mistake to Avoid: Replacing the sensor before verifying wiring harness continuity, supply voltage, and ground connection.
Frequently Asked Questions — P3402 DTC
What does OBD-II code P3402 mean?
Code P3402 stands for 'Manufacturer Specific (GMC) Auxiliary Emission Controls DTC P3402'. It indicates an issue detected by the powertrain or control module within the Auxiliary Emission Controls.
Can I continue driving with code P3402 active?
Safe to drive to a repair shop or home, but arrange inspection soon to maintain optimal efficiency and pass emissions.
What are the most common causes of code P3402?
The most frequent root causes include: Faulty or degraded sensor related to auxiliary emission controls, Damaged, corroded, or loose wiring harness connector, Intermittent short circuit or open circuit to ground / reference voltage.
How much does it typically cost to fix code P3402?
The average repair cost for code P3402 ranges from $65 – $420, depending on whether it requires a basic sensor replacement, wiring repair, or major mechanical component.