OBD-II Diagnostic Trouble Code
P1037 — NOx Sensor Bank 1 Sensor 1
P1037 is a manufacturer-specific code; the most common meaning is a fault with NOx sensor bank 1 sensor 1, the upstream NOx sensor ahead of the SCR catalyst. The ECM detected that the sensor reading or its data link communication is out of range or implausible. Exact meaning varies by OEM.
Severity 4/5
Truck-relevant
Stop within 50 mi
Severity
Stop within 50 mi
NOx Sensor Bank 1 Sensor 1
Code
P1037
Category
Powertrain
Subsystem
Aftertreatment
Truck-relevant
Yes
What this means for truckers
P1037 (NOx Sensor Bank 1 Sensor 1) — upstream NOx sensor performance issue. P1xxx variant of the standard NOx sensor code family. Same fix path: clean sensor first, replace if scan data confirms.
Before you replace parts — try this first
P1037 on the Aftertreatment system is most often failed upstream nox sensor — not a dead part. On commercial diesels especially, work these in order before spending money on parts:
- Confirm the symptoms. Match what your truck is doing to the Symptoms section below. If the code is set but the symptoms are not there, clear the code and re-test after a drive cycle — it may not return.
- Clean and dry the sensor connector. Water, road salt, or oil seeping into a connector is the #1 fake sensor failure. Disconnect, look for green corrosion or moisture, spray with electrical contact cleaner, dry, reseat. Many faults clear here for $0.
- Inspect the wiring harness. Trace the wire from the sensor toward the ECM — look for chafing against the engine block, melted insulation near the turbo or exhaust, or pinch points where a clamp has rubbed through.
- Test the sensor before swapping it. Most Common Causes (below) list the expected voltage or resistance range — a $20 multimeter saves a $300 sensor swap that does not fix the problem.
- Only then, replace the part. Use the OEM or a tier-1 aftermarket. Cheap sensors throw the same code in two weeks.
Symptoms
Check-engine light, possible DEF dosing problems and in some trucks an emissions derate timer. Fuel economy is usually unaffected.
Common causes
- CommonFailed upstream NOx sensor ($500–$1200)
- CommonDamaged wiring or connector ($150–$500)
- OccasionalExhaust leak near the sensor ($150–$700)
- RareECM software issue ($150–$400)
How to fix
Check OEM service info for the exact code definition
When to use: First step since meaning varies by OEM
Inspect sensor wiring, power, ground and connector
When to use: Before replacing parts
Check for exhaust leaks
When to use: If the reading is implausible
Replace the NOx sensor
When to use: When the sensor fails testing
Affects most
No specific vehicle pattern found in our complaint database. This code can appear on any vehicle that supports OBD-II diagnostics.
Related
- → Browse all DTC trouble codes
- → Decode a VIN to check codes for your truck
- → Owner-operator maintenance guides
- → P1058 — NOx Sensor Heater Circuit Bank 1
- → P1093 — Fuel Rail Pressure Low During Power Enrichment
- → P1094 — Fuel Rail Pressure Sensor Performance
- → P10DE — Diesel Particulate Filter Soot Level Too High
- → P10DF — Diesel Particulate Filter Soot Level Too High - Service Required
Frequently Asked Questions
Can I drive with code P1037?
Drive with caution. P1037 is severity 4 — stop within ~50 miles. Most commercial diesel codes at this severity (turbo, fuel rail, transmission solenoid) can damage adjacent expensive components if left unrepaired. Get to a service location before highway-speed loads.
How much does it cost to fix P1037 on a commercial truck?
Total repair cost ranges $150–$1200 depending on the root cause. The cheapest fix is usually the first one listed below — Failed upstream NOx sensor — which is also the most common. On commercial trucks the cost is usually higher than passenger vehicles due to part availability and shop labor rates ($120–185/hour at most truck shops, vs $90–130 at general auto shops). DIY-capable fixes (sensors, hoses, filters) are at the low end; major component replacements (turbo actuator, high-pressure fuel pump, transmission solenoid pack) are at the high end. Always diagnose with a scan tool BEFORE replacing parts — guessing wrong on a $1,500 turbo actuator when the actual issue was a $30 boost hose is a common expensive mistake.
Will P1037 fail a DOT inspection?
Yes — P1037 is an emissions-related code, and DOT inspectors check emissions compliance. An active emissions code with a check engine light can result in an out-of-service violation under FMCSA Part 393. The truck typically can't be moved until the code is cleared. Repeated emissions violations escalate to CSA scores.
What's the difference between P1037 and related codes?
P1037 is closely related to: P1058 (NOx Sensor Heater Circuit Bank 1), P1093 (Fuel Rail Pressure Low During Power Enrichment), P1094 (Fuel Rail Pressure Sensor Performance), P10DE (Diesel Particulate Filter Soot Level Too High). These codes share the same subsystem (aftertreatment) and often appear together. If you see this code, scan for the full code list — fixing the root cause usually clears multiple companion codes at once. If only P1037 is set without the companions, the issue is more isolated.
How do I prevent P1037 from coming back after a repair?
For P1037 (NOx Sensor Bank 1 Sensor 1), prevention centers on the aftertreatment system. Run quality DEF (verify supplier — BlueDEF, PEAK, Yara Air1). Don't skip parked regens — when the dash asks for one, do it. Avoid extended idle time which fouls the DPF. Replace NOx sensors at the OEM interval (typically 400K miles).