Exhaust Gas Temperature Sensor Circuit Bank 2 Sensor 1 Low (Generic)
The P4009 code means the vehicle's onboard diagnostic system has detected: Exhaust Gas Temperature Sensor Circuit Bank 2 Sensor 1 Low (Generic). This is a moderate severity code.
- Keep driving?
- Short distances only
- DIY difficulty
- hard
- Estimated cost
- $100 - $400 (parts and labor)
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Common Symptoms
- Check Engine Light on
- Low temperature reading on bank 2
- Asymmetric DPF regeneration
- Slight power reduction
Probable Causes (Ranked by Likelihood)
- Short to ground in bank 2 EGT sensor 1 circuit Very High
- Faulty sensor reading low High
- Corrosion in connector Moderate
- Ground circuit fault Low
Step-by-Step Diagnostic Procedure
-
Measure sensor resistance and compare to specification
-
Check for shorts to ground in wiring
-
Inspect connector for corrosion
-
Compare bank 1 and bank 2 sensor readings for consistency
Frequently Asked Questions
Can I drive with P4009?
You can drive short distances but DPF regeneration may not function correctly on bank 2, leading to potential DPF clogging.
How do I compare bank 1 and bank 2 readings?
With the engine at operating temperature, both bank 1 and bank 2 pre-DPF EGT sensors should read within about 50 degrees F of each other at steady state.
What does short to ground mean?
It means the sensor signal wire is making contact with a ground point, pulling the voltage to zero. This is usually caused by damaged wiring insulation touching the frame or exhaust.
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