OBD-II Code
P0477
Severity
Not yet reviewed
Nobody on our side has assessed this code yet, so we are not going to guess at how serious it is.
Can you drive it
We cannot say
Treat it as unknown until a shop reads it with live data. If the check-engine light is FLASHING, stop driving as soon as it is safe to — that means an active misfire, whatever the code.
Indicative cost (USD)
$30–$900
From this code's diagnostic notes. Varies by vehicle, diagnosis, parts, and local labor. This is not a repair quote.
$30 (pigtail repair) to $900 (actuator + harness + active regen on a Cummins).
P0477 means the Exhaust Back Pressure Control Valve circuit is reporting low — the ECM commanded the valve actuator to draw current and the current draw or driver voltage came in below the expected threshold.
How a shop works this
Work from evidence to part, not the other way round. A code names a circuit or a symptom; it does not name the part that failed.
Note every code that is set, not just this one.
Codes that appear together usually narrow the cause faster than any one of them read alone.
Read the freeze frame — the conditions the fault was recorded under.
Cold or warm, idle or load, road speed and engine speed. A fault that only appears cold is a different fault from one that only appears under load, even with the same code on the scanner.
Confirm the fault is current rather than history.
Clear the code and see whether it returns under those same conditions. A code that does not come back may have been logged during a repair, a flat battery, or a bad connection that has since been disturbed.
Then follow the diagnostic notes further down this page, in the order they are written.
They are written in the order a shop works this code, cheapest checks first. Where they name a component, inspect its wiring and connector before replacing it.
If the code comes back after a repair, the underlying fault is still there. That is the point to bring in a scanner with live data and freeze-frame, or a shop that has one.
Common symptoms
- Check engine light
Read the full diagnostic procedureP0477 means the Exhaust Back Pressure Control Valve circuit is reporting low — the ECM commanded the valve actuator to draw current and the current d…
P0477 means the Exhaust Back Pressure Control Valve circuit is reporting low — the ECM commanded the valve actuator to draw current and the current draw or driver voltage came in below the expected threshold. This typically means an open circuit between the ECM driver and the actuator coil, a high-resistance connection, or an internally-open actuator winding.
Cheapest-first ladder
- Unplug the valve connector and inspect for corrosion, soot ingress, or bent pins — diesel EBP connectors live in heat-soaked, vibration-heavy real estate and corrode from the inside. A $5 connector cleanup fixes 25% of P0477s.
- DMM resistance check across the actuator coil terminals — most EBP actuator coils measure 1-5 ohms across the windings; infinite resistance means an open coil (replace actuator), 0 ohms means shorted winding, intermittent reading on wiggle is a broken winding internal to the actuator.
- Backprobe the harness with the connector unplugged and key on: should see battery voltage on the supply pin and a clean low-side return through the ECM driver when commanded. Compare against expected current draw of 0.5-2.0A during bidirectional command.
- Inspect the harness for chafe at the actuator bracket and at any heat-shielded sections — a partial conductor break shows up as low current without a hard open. Expensive-misdiagnosis caveat: diesel EBP valves seize from soot accumulation and present as 'low circuit' because the actuator can't physically move and the ECM interprets the stalled current draw as low — clean before replacing; a $20 cleaning saves the $300 valve. Run an active regen first to clear the buildup if scan tool supports it.
Vehicle-specific patterns2003-2007 Ford 6.0L Powerstroke throws P0477 most often from a corroded actuator pigtail at the EBP valve — Ford routes the harness past the up-pipe…
- 2003-2007Ford 6.0L Powerstroke throws P0477 most often from a corroded actuator pigtail at the EBP valve — Ford routes the harness past the up-pipe and the connector cooks; resleeving and re-pigtailing is the standard repair.
- 2008-2010Ford 6.4L Powerstroke shows similar pigtail issues.
- 2007-2016Duramax LMM/LML uses the EGR cooler bypass valve actuator and throws functionally similar circuit-low codes when the actuator harness fatigues at the heat shield.
- 2007-2018RAM Cummins 6.7L VGT actuator is wired with a sealed connector that fails when the gasket inside the connector hardens and lets in moisture; the actuator itself is robust but the connector kills it.
- 2009-2014VW 2.0 TDI EGR throttle actuator commonly fails with a circuit-low symptom when the internal motor brushes wear out. Common diesel concern: soot-bound EBP valves from extended highway non-regen cruise can mimic circuit-low — recommend active regen via scan tool first.
Estimated repair$30 (pigtail repair) to $900 (actuator + harness + active regen on a Cummins).
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