Description
Inlet (upstream) NOx sensor for Mack and Volvo MP/D-platform heavy-duty diesel engines — PAI 853761. Mounts upstream of the SCR catalyst and reports raw exhaust NOx to the aftertreatment ECU for closed-loop DEF dosing control. The 4-pin rectangular connector, M20 × 1.5 exhaust boss, and 23″ overall harness length match Mack OEM 21636091 and Mack/Volvo 22303390.
Signs You Need a New NOx Sensor
- Aftertreatment fault codes referencing the upstream / inlet NOx sensor (SPN 3216, 3226, or related)
- SCR efficiency derate or torque limit triggered by NOx-related DTCs
- DEF dosing rate that no longer correlates with engine load
- MIL or check-engine warning with NOx sensor heater circuit faults
Specifications
| Manufacturer | PAI Industries |
|---|---|
| Part Number | 853761 |
| Part Type | Inlet NOx Sensor (upstream of SCR) |
| Connector | 4-pin rectangular |
| Thread | M20 × 1.5 exhaust boss |
| Harness Length | 23 in (584 mm) overall |
Cross References
This sensor replaces or is equivalent to the following part numbers:
- Mack: 20958942, 21227721, 21302275, 21346959, 21479638, 21567764, 21636091
- Mack / Volvo: 22303390
Applications
This inlet NOx sensor fits the SCR aftertreatment system on Mack and Volvo on-highway and vocational trucks running:
- Mack MP7 / MP8 (EPA10 and later)
- Volvo D11 / D13 / D16 (EPA10 and later)
Representative chassis: Mack Pinnacle, Granite, Anthem, CHU/CXU; Volvo VNL, VNR, VNX, VHD.
Verify the sensor is in the inlet (upstream) position — Mack/Volvo also use a different outlet NOx sensor downstream of the SCR catalyst with similar appearance but different OEM number. After installation, an aftertreatment relearn / DEF system reset may be required.
