P2A38: O2 Sensor Positive Current Control Circuit/Open Bank 1 Sensor 3

P2A38 reports that the lead carrying positive current control for bank 1's third oxygen sensor has no continuity. That sensor sits behind a second converter or a later aftertreatment stage, and the code only makes sense where this position carries a wide-band probe: through this lead (pin APE/IP on a Bosch LSU 4.9) the controller drives between about −2 and +2.25 mA into the pump cell. No manufacturer documents P2A38 publicly. For the upstream twin P2237, Ford's 2012 summary spots a broken IP wire because lambda barely moves during deliberate reference-current pulses; its own third sensors are switching types with heater codes only. P2A39/P2A3A are the low/high faults, P2A3B the open return. The lamp lights, while driving feels unchanged.

Bank 1 is the side of the engine with cylinder 1. Inline engines only have this bank.

Symptoms

• Check engine light
• Sensor 3 value frozen near lambda 1 in live data
• Downstream emission monitors not completed

Most likely causes

• Broken pump-current wire or pushed-back pin in the sensor plug
• Sensor plug loose or not latched after exhaust work
• Internal break in the pump cell of the probe

What to check, in order

Start with the simplest. You can tick off each step.

1. Check the wiring and connector of the sensor indicated
2. Check the continuity of the wire between the component and the control module.
3. Look for exhaust leaks
4. Check the signal in live data with the engine warm
5. Check the fuse and the heater resistance if the code mentions it
6. Replace the sensor if it has power and does not respond

Good to know

• Repair difficulty: medium
• It affects emissions.

What each character of P2A38 means

• P: Powertrain: engine and transmission
• 2: Generic code: same on every make
• A: Hybrid or air and fuel
• 38: Specific fault in that system

Frequently asked questions

Can I keep driving with code P2A38?

Yes, you can normally drive in moderation, but get it repaired soon: you will use more fuel and the catalytic converter can be damaged over time.

What causes code P2A38?

The most common causes are: broken pump-current wire or pushed-back pin in the sensor plug; sensor plug loose or not latched after exhaust work; internal break in the pump cell of the probe.

Related codes

• P2A39O2 Sensor Positive Current Control Circuit Low Bank 1 Sensor 3
• P2A3AO2 Sensor Positive Current Control Circuit High Bank 1 Sensor 3
• P2A3BO2 Sensor Negative Current Control Circuit/Open Bank 1 Sensor 3
• P22ABO2 Sensor Positive Current Control Circuit/Open (Bank 1 Sensor 2)
• P2237O2 Sensor Positive Current Control Circuit/Open (Bank 1 Sensor 1)
• P0142O2 Sensor Circuit Bank 1 Sensor 3

Sources

• newtonnet.co.uk: fordobd2012
• bosch-motorsport.com: Data Sheet 69034379 Lambda Sensor LSU 4.9
• law.cornell.edu: 13 CCR 1968.2

Values and procedures vary by manufacturer. If it affects brakes, steering, fuel or high voltage, see a professional. Updated: 2026-11-04. How we build these pages.