O2 Sensor Positive Current Control Circuit/Open Bank 1 Sensor 1
P2237 indicates the PCM detected a malfunction in the positive current control circuit of the Bank 1 Sensor 1 oxygen sensor (upstream O2 sensor). This sensor monitors exhaust oxygen levels to help the engine maintain proper fuel mixture; and a circuit fault prevents accurate readings from reaching the engine computer.
What You Might Notice
- Check Engine Light or Service Engine Soon lamp illumination
- Reduced fuel economy
- Diminished engine performance or hesitation
- Stored misfire codes or lean/rich exhaust condition codes
- Rough idle or stalling
Most Common Causes
- 1
Defective Bank 1 Sensor 1 O2 Sensor
The oxygen sensor itself has failed electrically or internally, preventing proper voltage output to the PCM. This is the most common cause of P2237.
- 2
Wiring or Connector Issues
Corroded, damaged, or loose wiring/connectors in the O2 sensor circuit can interrupt signal transmission to the PCM.
- 3
PCM or Engine Control Module Malfunction
A faulty PCM unable to properly read the O2 sensor signal may set this code even if the sensor is functioning correctly.
- 4
Exhaust Leak Near O2 Sensor
An exhaust leak upstream of the O2 sensor allows outside oxygen to enter, causing erratic voltage signals the PCM interprets as a circuit fault.
How to Diagnose It
- 1
Check Defective Bank 1 Sensor 1 O2 Sensor — The oxygen sensor itself has failed electrically or internally, preventing proper voltage output to the PCM. This is the most common cause of P2237.
- 2
Check Wiring or Connector Issues — Corroded, damaged, or loose wiring/connectors in the O2 sensor circuit can interrupt signal transmission to the PCM.
- 3
Check PCM or Engine Control Module Malfunction — A faulty PCM unable to properly read the O2 sensor signal may set this code even if the sensor is functioning correctly.
- 4
Check Exhaust Leak Near O2 Sensor — An exhaust leak upstream of the O2 sensor allows outside oxygen to enter, causing erratic voltage signals the PCM interprets as a circuit fault.
How to Fix It
- 1
Replace Bank 1 Sensor 1 O2 Sensor
Remove the faulty upstream oxygen sensor and install a new OEM or quality aftermarket replacement. This resolves the fault in the majority of cases.
- 2
Inspect and Repair Wiring and Connectors
Check the O2 sensor wiring harness and connectors for corrosion, damage, or loose connections. Clean corroded contacts or replace damaged wiring as needed.
- 3
Check for Exhaust Leaks
Inspect the exhaust manifold and components upstream of the O2 sensor for cracks or leaks. Repair or replace any leaking exhaust components.
- 4
Test and Replace PCM if Needed
If the O2 sensor, wiring, and exhaust are all sound, the PCM may be faulty. Have the module tested or replaced by a qualified technician.
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