Diesel Oxidation Catalyst Temperature Sensor Circuit High (Generic)
The P4084 code means the vehicle's onboard diagnostic system has detected: Diesel Oxidation Catalyst Temperature Sensor Circuit High (Generic). This is a moderate severity code.
- Keep driving?
- Short distances only
- DIY difficulty
- hard
- Estimated cost
- $80 - $350 (parts and labor)
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Common Symptoms
- Check Engine Light on
- False high DOC temperature
- Premature DPF regen initiation
- Poor fuel economy from excess regen
- Possible DOC overheat protection
Probable Causes (Ranked by Likelihood)
- Short to voltage in DOC sensor circuit Very High
- DOC sensor failure reading high High
- Wiring chafed near DOC Moderate
- Reference voltage fault Low
Step-by-Step Diagnostic Procedure
-
Check DOC sensor voltage against specification
-
Disconnect sensor and check for stray voltage
-
Inspect wiring for heat damage
-
Verify reference circuit
Frequently Asked Questions
Can P4084 cause unnecessary DPF regen?
Yes, a false high reading may cause the PCM to think the DOC is ready for regen before it actually is.
Can I drive with P4084?
You can drive short distances but fuel economy will suffer from excessive regeneration events.
Is the DOC sensor expensive?
The sensor is typically $40-100. With labor near the DOC, expect $100-350 total.
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