Fix P0163: Mechanic’s solutions that WORKED

The P0163: O2 Sensor Circuit Low Voltage (Bank 2 Sensor 3) code signifies that the oxygen sensor circuit is reporting a lower than expected voltage, specifically in the third sensor on bank 2. This issue can stem from a defective sensor, wiring problems, or an exhaust leak.

P0163 quick overview

Meaning	P0163: O2 Sensor Circuit Low Voltage (Bank 2 Sensor 3)
Is it serious?	Yes, as it can result in suboptimal engine performance, increased emissions, and potential harm to the catalytic converter over time.
Possible causes	– Faulty oxygen sensor – Short to ground in the sensor wiring or connectors – Exhaust leaks affecting sensor readings – Problems with the fuel delivery system – Faulty ECM
How to diagnose?	Inspect the O2 sensor and wiring for any visible damage or shorts. Measure the sensor’s voltage output with a multimeter or scan tool. Check for exhaust leaks that could skew the sensor’s readings. Evaluate the fuel delivery system for issues causing a lean mixture. Seek professional assistance for ECM diagnosis or repair.

How to fix P0163 – learn from mechanics

I looked into P0162 – P0167 (Bank2 Sensor3) service cases at iatn.com website where in the private forums the mechanics seek advice from other mechanics. These codes are unfortunately very rare and there weren’t that many cases. Check these 4, but remember that you want to fix other engine issues before diagnosing oxygen sensors.

Case #1: Nissan

Vehicle Information 1999 Nissan Pathfinder LE 3.3L

Issue + Repair History

• MIL Lamp on
• Code P0160: Bank 2 Sensor 2 voltage high
• Previous repair: Hard ground wire kit installed to ground intake to block

Other OBD2 Codes + Test Results

• Manifold Vacuum Readings: 18 in. at idle

Suggestions to Fix Issue

• Check for a shorted sensor or faulty ground
• ECM under federal warranty, consider replacing ECM and rear O2 sensor
• Verify if ECM can be reprogrammed instead of replaced

Final Fix

• Replaced ECM under federal warranty and rear O2 sensor, which resolved the issue

Case #2: Ford

Vehicle Information 2009 Ford F-350 Super Duty FX4 6.8L

Issue + Repair History

• No start issue
• PCM doesn’t turn on fuel pump adequately
• Replaced fuel pump, fuel pump driver module, and fuel pressure regulator
• Codes: C1703, 1701,1704,1709, 1705, 1706, 1700, 9-u codes, B2900, B1318, P0113, P0191, P0416, P0453, P0162, P1233

Suggestions to Fix Issue

• Check for corrosion at the Fuel Pump Control Module (FPCM) and replace if necessary
• Verify power to the pump and current ramp fuel pump
• Check for faulty Powertrain Control Module (PCM) or wiring issues
• Ensure proper ground for FPCM
• Check rail pressure sensor and its connection to the PCM
• Consider bypassing the FPDM to test if the fuel pump runs at maximum capacity

Final Fix

• Found and repaired a faulty connector (C110) which was causing intermittent voltage issues
• Replaced a bare wire in the harness with a coated wire
• Bypassed the wire from the inertia switch to the FPDM to turn on the pump
• Cut and reconnected the wire feeding the fuel sending unit to restore fuel gauge functionality

Case #3: Audi

Vehicle Information 2001 Audi A6 Quattro 2.7L

Issue + Repair History

• Coolant leak led to intake manifold removal and aux water pump replacement
• MIL and ABS lights came on during road test with loss of power
• Codes: P1392, P1338, P1633, P0237, P0166

Suggestions to Fix Issue

• Check wiring connections around the manifold for open or short to B+ circuit codes
• Ensure ECU grounds are reconnected at intake manifold and throttle body is plugged in
• Look for a ground problem at the intake manifold, checking for wires that may have been missed during reassembly
• Double-check the sensor directly under the intake and at the rubber boot for pinched wires

Final Fix

• Found a self-inflicted issue: a cracked connector and bent wiring on the camshaft sensor caused by accidental bumping during manifold reassembly, leading to a shorted circuit and the activation of warning lights

Case #4: Hyundai

Vehicle Information 2003 Hyundai Sonata GLS 2.7L

Issue + Repair History

• Symptoms: Poor idle quality, misfire, MIL lamp on
• Same symptoms occurred a year ago
• EVAP valve cleaned, MAF cleaned previously
• Current situation: Codes present but motor runs well after reset, problem reoccurs after a few days
• Diagnosis: No vacuum leak, purge valve not stuck open, normal fuel pressure, original spark plugs in poor condition, severe sludge build-up inside valve covers

Suggestions to Fix Issue

• Disconnect Purge Control valve and check fuel trims
• Replace MAF sensor
• Check intake gasket for leaks
• Replace tune-up parts (plugs and wires)
• Smoke test for vacuum leaks when cold
• Perform cylinder leak down test
• Replace or clean MAF sensor again

Final Fix

• Replaced tune-up parts, primarily plugs and wires
• Engine ran well with no codes and fuel trims back to near zero
• Sludge build-up due to infrequent oil changes by owner, no action taken to remove sludge due to potential harm

Advice	Diagnostic Step
Check for vacuum leaks	Inspect all vacuum lines and intake manifold for leaks, as these can affect oxygen sensor readings.
Inspect wiring and connectors	Examine the wiring and connectors related to the oxygen sensor for damage or corrosion.
Verify proper fuel pressure	Ensure the fuel pressure is within the manufacturer’s specifications.
Check other related sensors	Diagnose related sensors like MAF, MAP, and fuel trim sensors, as their malfunction can affect O2 readings.
Perform a smoke test	Conduct a smoke test to identify any hard-to-find vacuum leaks.
Inspect the condition of spark plugs	Worn or dirty spark plugs can cause misfires, affecting O2 sensor readings.
Address any maintenance neglect	Resolve any long-standing maintenance issues, such as oil sludge or overdue tune-ups.
Consider a PCM/ECM reflash or update	Sometimes, updating the vehicle’s computer software can resolve sensor-related issues.
Test related components before O2 sensor	Diagnose and rule out issues with related components before concluding the O2 sensor is at fault.