Bosch 13231 Oxygen Sensor - Upstream

Bosch OE Oxygen Sensor for BMW Upstream Applications

Bosch 13231 is an Actual OE Oxygen Sensor built for precise air-fuel ratio feedback in narrow-band, heated applications. It is a specific-fit replacement for select BMW upstream positions, including 1987-1995 BMW 325i, 318i, 318is, 318ti, M3, 740i, 740iL, 750iL, and related models.

Using a threaded metal housing, 4-wire configuration, and integrated wiring harness, this Bosch oxygen sensor is made for stable closed-loop operation and accurate ECU input across changing exhaust temperatures. Bosch’s OE sensor development includes narrowband designs with faster light-off and improved lambda accuracy for dependable emissions control.

Key Features

• Actual OE Oxygen Sensor from Bosch
• Narrow-band heated sensor design for upstream exhaust monitoring
• Specific fit for select BMW applications
• 4-wire, pin-terminal, female connector configuration
• Threaded mounting with 18 mm thread diameter and 22 mm hex size
• Metal housing with integrated wiring harness
• Wiring harness length: 18.7 in; overall length: 22.4 in
• Standard replacement grade for emission control service

Product Details

Bosch 13231 is engineered for vehicles that rely on a narrow-band heated oxygen sensor to report exhaust oxygen content to the ECU. That signal helps the engine manage fuel delivery, combustion stability, and emissions performance. This part cross-references Bosch OE-style applications for the same use case, including BMW 11781247235 and 11781702931.

For BMW owners searching for an upstream oxygen sensor for 1992-1995 BMW 318i, 1989-1995 BMW 325i, or 1993-1994 BMW 740iL, Bosch 13231 provides the OE-style sensor architecture expected in these applications. It is also listed for 1995 BMW M3 and other select BMW models with exact-fit requirements.

What It Helps Address

• Check engine light related to oxygen sensor performance
• Rich or lean fuel mixture readings at the ECU
• Unstable closed-loop fuel control after sensor aging
• Slow sensor response during warm-up or normal operation
• Emissions test failures tied to upstream sensor output

Installation Notes

Install Bosch 13231 in the upstream position only where listed in the fitment data. Confirm the connector shape, 4-pin terminal layout, 18 mm thread size, and harness length before installation. The sensor uses a threaded mount and female connector; verify the vehicle’s original routing and exhaust bung condition before tightening.

• Fits 1987 BMW 325i, Upstream
• Fits 1988 BMW 325i, Upstream
• Fits 1988 BMW 325is, Upstream
• Fits 1988-1994 BMW 750iL, Upstream
• Fits 1988-1991 BMW 325iX, Upstream
• Fits 1989-1995 BMW 325i, Upstream
• Fits 1989-1995 BMW 325is, Upstream
• Fits 1991-1992 BMW 850i, Upstream
• Fits 1992-1995 BMW 318i, Upstream
• Fits 1992-1995 BMW 318is, Upstream
• Fits 1993-1994 BMW 740i, Upstream
• Fits 1993-1994 BMW 740iL, Upstream
• Fits 1993-1994 BMW 850Ci, Upstream
• Fits 1994 BMW 530i, Upstream
• Fits 1994 BMW 540i, Upstream
• Fits 1994 BMW 840Ci, Upstream
• Fits 1994-1995 BMW 850CSi, Upstream
• Fits 1995 BMW 318ti, Upstream
• Fits 1995 BMW M3, Upstream

Quality Assurance

Bosch has more than five decades of OE oxygen sensor development behind this part. The sensor uses advanced ceramic elements, controlled heater operation, and high-temperature-resistant materials to maintain consistent performance under heat and vibration common in exhaust service.