Mercedes-Benz NOx Sensor A0009057208 Pinout, Connector Details, Wire Colors

User question

I need the pinout for a nox sensor with this Reference A0009057208

Artificial Intelligence Response

Direct answer to the question

• Mercedes-Benz NOx sensor A000 905 72 08 (Continental/Vitesco 5WK 97424, SNS424A) uses a 6-cavity Micro-ISO (MQS) connector, but only four pins are populated and active.
• The functional pinout (viewed on the harness/loom side with the latch at the top) is:

 3 2 1 ── top row
6 5 4 ── bottom row

Pin	Typical wire colour*	Function
1	Red or Red/Yellow	+UBatt (12 V / 24 V)
2	Brown	Chassis / sensor ground (GND)
3	Green or Green/White	CAN-High (CAN_H)
4	White or White/Brown	CAN-Low (CAN_L)
5	— (sealed)	Not connected / supplier reserved
6	— (sealed)	Not connected / shield drain on some truck versions

*Wire colours can differ by platform and VIN; always confirm in WIS.

Detailed problem analysis

1. Sensor architecture
   • Smart, closed-loop NOx probe with an integrated control unit (ICU) on the back shell.
   • Zirconia pump cell + diffusion chamber measure O₂ and NOx; MCU inside the ICU performs heater control, signal conditioning, CAN protocol, and diagnostics.
   • Because the heater driver and measurement electronics are internal, only power, ground and differential CAN are exported—hence the 4-wire interface.

2. Electrical characteristics
   • Supply voltage: 9 – 16 V (passenger cars) or 18 – 32 V (HD trucks, same pinout).
   • In-rush heater current: ≈ 3 A for < 2 s; steady ≈ 0.6–0.8 A.
   • CAN: ISO 11898-2, typically 500 kbit/s, 60 Ω bus resistance (2 × 120 Ω terminators).

3. Typical diagnostic DTCs
   P2200, P229F, P229E – general NOx sensor circuit; U029D – CAN communication lost; P20EE – SCR efficiency (may be triggered by faulty NOx readings).

4. Common failure modes
   • Contaminated sensing element (coolant/oil leak, sulphur).
   • Heater burnout due to over-voltage or poor heat sinking.
   • Water ingress or corrosion in connector → high resistance on Pin 2, CAN errors.

Current information and trends

• EU-7 and EPA 2027 proposals push for faster light-off and ammonia sensing; Vitesco “multi-species” sensors now add NH₃ on the same 4-wire bus.
• Automotive Ethernet (100BASE-T1) prototypes exist but CAN-FD (2 Mbit/s) is the near-term upgrade path.
• Cyber-security (ISO 21434) now required: firmware integrity checks inside the NOx sensor ECU.

Supporting explanations and details

Practical pin checks (harness side, sensor unplugged):
• Resistance Pin 1 ↔ 2 ≈ < 2 Ω (wire only).
• Voltage Pin 1 ↔ 2 with IGN ON ≈ UBatt.
• Resistance Pin 3 ↔ 4 with battery disconnected ≈ 60 Ω (checks CAN pair).
Scope pattern: CAN_H 2.5 ↔ 3.5 V, CAN_L 2.5 ↔ 1.5 V, mirrored.

Ethical and legal aspects

• Sensor tampering or emulator “delete” kits violate EU 715/2007, US Clean Air Act, and most national MOT/periodic-inspection rules.
• Heater circuit bypass can start wiring fires; always retain factory fuse path (MB fuse F32-5, 15 A typical).
• Firmware and calibration data are OEM intellectual property—cloning or reverse-engineering for commercial use is prohibited.

Practical guidelines

Installation / replacement:

1. Disconnect battery negative.
2. Use penetrating oil; if seized, prefer induction heater over open flame.
3. Torque probe to 50 N·m (M20 × 1.5) with copper-based anti-seize.
4. Route harness away from exhaust, maintain ≥ 25 mm clearance.
5. Clear DTCs and perform SCR/NOx sensor relearn (XENTRY: “Initial startup of component NOx sensor downstream”).

Field tests after replacement:
• Monitor live NOx value: idle < 80 ppm, cruise 30–50 ppm (Euro-6 diesel in good condition).
• ICU temperature reach > 650 °C within 90 s of start.
• CAN traffic present at IDs 0x18DAF1xx (diagnostic) and 0x0CB / 0x18FEF1xx (measurement).

Possible disclaimers or additional notes

• Some heavy-duty MB trucks use the same core sensor with 24 V supply; pin numbers identical but wire colours and fuse ratings differ.
• Rare aftermarket harnesses flip the cavity numbering (viewed from sensor side)—always reference cavity numbers embossed on connector.
• Sensor is non-serviceable; attempts to clean or bench-heat usually destroy the diffusion barrier.

Suggestions for further research

• SAE 2022-01-0541: “Next-generation smart NOx sensors for Euro-7”.
• Vitesco datasheet SNS1006A v1.2 (2023-06) for cross-reference current draw and CAN IDs.
• Mercedes-Benz WIS documents: AR07.10-P-0050-97A (connector layout) and GF14.40-P-0018-97A (NOx function description).
• ISO 21434 and UNECE R155 for cyber-security implications on exhaust-aftertreatment ECUs.

Brief summary

A000 905 72 08 is a four-wire, six-cavity smart NOx sensor: Pin 1 = Battery +, Pin 2 = Ground, Pin 3 = CAN-High, Pin 4 = CAN-Low (Pins 5–6 unused). The integrated control unit manages the heater internally and communicates over CAN. Correct wiring, clean grounds, and proper torque during installation are essential to ensure accurate emissions control and regulatory compliance.

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