OBD-II Code
P1127
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)
$5–$200
From this code's diagnostic notes. Varies by vehicle, diagnosis, parts, and local labor. This is not a repair quote.
P1127 on a Toyota means the ETCS Actuator Power Source Circuit has detected a fault in the dedicated power supply that feeds the throttle motor H-bridge driver — there's a separate ETCS power feed (typically through a dedicated ETCS relay and fuse, often labeled ETCS or THR on the underhood fuse box) and when battery voltage at that node drops outside spec or the relay fails to energize on key-on, P1127 sets.
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 procedureP1127 on a Toyota means the ETCS Actuator Power Source Circuit has detected a fault in the dedicated power supply that feeds the throttle motor H-bri…
P1127 on a Toyota means the ETCS Actuator Power Source Circuit has detected a fault in the dedicated power supply that feeds the throttle motor H-bridge driver — there's a separate ETCS power feed (typically through a dedicated ETCS relay and fuse, often labeled ETCS or THR on the underhood fuse box) and when battery voltage at that node drops outside spec or the relay fails to energize on key-on, P1127 sets. Voltage threshold is usually <8V or >18V for >2 seconds during key-on.
Cheapest-first ladder
- check the ETCS fuse first — it's a 10A or 15A fuse depending on platform, takes 60 seconds to inspect, and is the #1 P1127 cause.
- Back-probe the ETCS power feed at the throttle body connector with KOEO and KOER and confirm 12-14V; below 11V at the connector with 12.6V at the battery means voltage drop through corroded wiring or a tired relay.
- Swap the ETCS relay with an identical-pinout relay from the fuse box (commonly the same as the horn or fuel-pump relay on Toyota) and clear the code — if it stays away, the relay was the failure. Expensive-misdiagnosis caveat: don't replace the throttle body for P1127 — the motor and TPS inside the throttle body are downstream of the fault, not the cause; a $4 fuse or $25 relay fixes this code roughly 70% of the time on Toyota platforms, and a $400 throttle body replacement here is a pure waste.
Vehicle-specific patterns2002-2011 Toyota Camry 2.4L (2AZ-FE) and 3.0/3.5L (1MZ-FE, 2GR-FE) are common P1127 platforms — the ETCS relay sits in the underhood fuse box and fai…
- 2002-2011Toyota Camry 2.4L (2AZ-FE) and 3.0/3.5L (1MZ-FE, 2GR-FE) are common P1127 platforms — the ETCS relay sits in the underhood fuse box and fails from heat-cycle fatigue around 100K-150K mi.
- 2004-2010Highlander 3.3/3.5L (3MZ-FE, 2GR-FE) and Sienna 3.3/3.5L share the same relay and the same failure mode.
- 2003-2008RAV4 2.4L (2AZ-FE) and 2006-2012 RAV4 2.5L (2AR-FE) throw P1127 with the same root cause; the fuse-box location moves slightly between generations but the diagnostic is identical.
- 2001-2005Lexus IS300 and GS300 with the 2JZ-GE throw P1127 from a related ETCS-power wiring failure at the bulkhead connector, where harness chafe is the more common root cause than the relay.
Estimated repair$5 to $200.
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