P229E
NOx Sensor Heater Control Circuit Bank 1 Sensor 2P229E is a generic OBD-II powertrain diagnostic trouble code: NOx Sensor Heater Control Circuit Bank 1 Sensor 2. It is logged by the engine control unit when the scr/adblue monitor detects that a specific fault threshold has been exceeded — typically resulting in the malfunction-indicator lamp (MIL / check-engine light) being illuminated.
What P229E means
P229E is an SAE generic powertrain diagnostic trouble code defined as NOx Sensor Heater Control Circuit — Bank 1 Sensor 2. It is set when the engine control module (ECM) or exhaust aftertreatment control module detects an electrical fault in the heater control circuit of the downstream NOx sensor (Sensor 2, located after the SCR catalyst on Bank 1). The NOx sensor heater is critical for bringing the sensing element to its operating temperature quickly, ensuring accurate NOx measurement for SCR/AdBlue dosing control.
The P229x code family covers heater circuit faults across both upstream and downstream NOx sensors on diesel SCR systems. P229E specifically targets the Sensor 2 (post-SCR) heater circuit and may indicate an open circuit, short to ground, short to voltage, or a current that falls outside the expected range. Because Sensor 2 provides the primary feedback signal for AdBlue injection efficiency, a heater fault directly impairs the system's ability to verify SCR conversion performance and meet emissions targets.
On most Euro 5/6 and EPA Tier 4 diesel vehicles, this code will illuminate the MIL and may trigger a NOx emissions-related warning lamp or message. Depending on jurisdiction and manufacturer calibration, repeated or persistent faults can lead to torque reduction or a diesel exhaust fluid (DEF) system lockout after a defined number of drive cycles.
Common causes
Most-frequently reported root causes when P229E is logged.
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1
Broken, corroded, or chafed wiring in the NOx sensor heater supply or ground circuit
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2
Faulty NOx sensor (internal heater element open or short circuit)
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3
Blown fuse protecting the NOx sensor heater power supply
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4
Corroded or loose connector at the Sensor 2 NOx sensor harness plug
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5
Failed aftertreatment control module (ACM) or ECM heater driver output
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6
High-resistance connection due to exhaust heat damage to the sensor harness
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7
Moisture/water ingress into the sensor connector causing intermittent short
Symptoms drivers notice
How to diagnose P229E
A typical diagnostic flow when this code is present.
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1
Retrieve all stored DTCs with a scan tool and record freeze-frame data; note any related P229x, P20EE, or P20xx SCR/NOx codes present
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2
Inspect the NOx Sensor 2 harness from the sensor connector back to the ACM/ECM for chafing, heat damage, corrosion, or broken wires
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3
Check the heater power supply fuse for the NOx sensor circuit; replace if blown and investigate root cause
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4
Measure heater circuit resistance at the sensor connector with the sensor unplugged
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5
With the sensor reconnected and ignition on/engine running, measure heater supply voltage at the connector
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6
Inspect the ACM/ECM heater control output pin for proper switching using a lab scope or test light
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7
Clear the DTC, perform a cold-start drive cycle to allow the heater to activate, and confirm whether the fault returns
Vehicles where we've handled P229E
Platforms in our catalogue with confirmed P229E coverage.
Related powertrain codes
- B0001 — PCM Discrete Input Speed Signal Error
- B0004 — PCM Discrete Input Speed Signal Not Present
- C0359 — Four Wheel Drive Low Range (4LO) Discrete Output Circuit
- C0362 — 4LO Discrete Output Circuit High
- P2000 — NOx Adsorber Efficiency Below Threshold Bank 1
- P2001 — NOx Adsorber Efficiency Below Threshold Bank 2
Frequently asked questions
Can I drive with a P229E code active?
Short-term driving is generally possible, but the SCR/AdBlue system cannot verify emissions performance without a working downstream NOx sensor heater. On many vehicles, sustained operation with this fault will eventually trigger a torque reduction or DEF lockout warning.
Will P229E cause my vehicle to fail an emissions test?
Yes, on most Euro 5/6 or EPA-compliant diesel vehicles. An active MIL combined with an SCR/NOx-related fault code is an automatic failure at emissions inspection.
Is P229E always a faulty NOx sensor, or could it be wiring?
Both are common. Always inspect the harness and connector first before condemning the sensor, as heat damage and corrosion to the wiring near the exhaust tunnel are frequent culprits.
What is the difference between P229E and P229F or P22A0?
P229E is heater circuit fault on Bank 1 Sensor 2 (post-SCR). P229F is typically an over-current condition on the same circuit, while P22A0 relates to circuit low on Bank 1 Sensor 2.
Disabling P229E in software
RaceTune can permanently disable P229E — and any other OBD-II diagnostic trouble code — on every ECU family we support. The monitor is disabled inside the ECU itself, so the fault stops being logged: the warning light stays off and the engine never enters limp mode for this code. The change is tied to your exact software version.
ECUs with a P229E disable in our catalogue
Confirmed coverage from our recipe database — we support many more families. Upload your file and our identifier will match it automatically.
- Bosch EDC17C74 verified 2 software versions
- Bosch EDC17CP57 verified 2 software versions
- Bosch EDC17C50 verified 1 software version
- Bosch EDC17C56 verified 1 software version
- Bosch EDC17C66 verified 1 software version
- Bosch EDC17CP44 verified 1 software version
- Bosch MD1CP002 verified 1 software version
- Bosch MD1CP004 verified 1 software version
Software modifications affect emissions compliance and are not road-legal in many jurisdictions. RaceTune service files are intended for motorsport, off-road, and export use.
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