What if I see both P2122 and P2127 at the same time?

Two pedal sensors failing simultaneously is unusual as a true coincidence. When P2122 and P2127 set together, the diagnostic focus shifts to shared wiring — most commonly a damaged ground wire that serves both sensors, or harness damage near the pedal connector that affected multiple conductors. Inspect the pedal connector carefully, look for water intrusion, check for pushed-back pins, and trace the ground wires from the pedal back to chassis ground. If shared wiring is healthy and both sensors are reading low independently, then the pedal assembly itself has failed — but verify wiring first because that's the cheaper repair.

Is the 'E' sensor more important than the 'D' sensor?

No — they're equally important by design. The 'D' and 'E' labels (or 'A' and 'B' on some platforms) are just two independent sensors inside the same pedal assembly, doing the same job redundantly. The PCM uses both to confirm pedal position. If one fails, the other still works but the PCM enters reduced-power mode because it can no longer cross-check the reading. There's no hierarchical difference — both are needed for normal operation, and a failure of either one produces similar driveability symptoms.

Can I keep driving with P2127?

Short distances only. The PCM has the throttle in reduced-power mode and won't let the engine make full power until the issue is resolved. That's fine for getting home or to a shop, but unsafe for highway driving because you can't merge or pass with the power limit. The code also doesn't tend to clear on its own — the failure is electrical, not weather-dependent or thermal — so the limp mode stays until the sensor or wiring is fixed.

How do I tell whether it's the wiring or the pedal?

Three-part test. First, with the sensor disconnected, verify 5V reference and clean ground at the harness-side connector pins for the 'E' circuit. If either is wrong, repair the wiring — that's likely your fix. Second, if reference and ground are healthy but the 'E' signal is still pegged low when connected, backprobe the signal wire at the PCM connector. If you see 0V at the PCM and the sensor is supposedly outputting a real value, the signal wire has an open or short somewhere between pedal and PCM. Third, if everything wires test good but the sensor reads pegged low when connected, the pedal assembly needs to be replaced. Wiring repairs are cheaper than pedal replacement, so always confirm the diagnosis before signing off on a pedal swap.

OBD-II trouble code

P2127: Throttle/Pedal Position Sensor 'E' Circuit Low Input

The 'E' position sensor inside the accelerator pedal assembly — the second of the two redundant sensors — is reporting near-zero voltage no matter where the pedal is. Paired sibling of P2122 but on the redundant sensor circuit.

Quick facts

System: Powertrain
Category: Throttle / Idle
Severity: High severity
Drivable: Usually safe to drive short-term
Repair cost range: $100 – $500
DIY difficulty: Intermediate DIY

What does P2127 mean?

P2127 is the redundant-sensor mirror of P2122. The accelerator pedal on a drive-by-wire vehicle contains two independent position sensors, often labeled 'D' and 'E' (or 'A' and 'B' on some platforms). Both report pedal position to the PCM on separate signal wires with separate reference and ground returns. The system is intentionally redundant for safety: if one sensor fails, the PCM has the other to fall back on, and the comparison between the two is the watchdog that catches unsafe situations.

P2127 sets when the 'E' sensor signal sits pegged near zero volts regardless of pedal position. Same electrical failure pattern as P2122, just on the second sensor circuit. The PCM treats the 'E' reading as untrustworthy, leans on the 'D' reading (if it's still healthy), and enters reduced-power mode to limit any risk from the partial failure.

Where this code becomes interesting is in pairing analysis. P2127 alone usually means the 'E' circuit failed — wiring or sensor on just that side. P2127 + P2122 together means both pedal sensors are reading low at the same time, which is unlikely as two independent failures and usually points at a shared wiring problem (often a damaged ground wire that serves both sensors, or harness damage near the pedal connector that affected multiple conductors). P2127 + P2138 means the 'E' sensor is hard-failed AND the correlation between D and E doesn't add up, which confirms a real sensor failure rather than a transient wiring glitch.

The diagnostic approach is the same as P2122 with the focus on the 'E' circuit pins instead of the 'D' circuit. The repair is usually the pedal assembly, since the two sensors are integrated and not serviceable individually on most platforms.

Common causes

Damaged or pinched wiring on the 'E' signal circuit between pedal and PCM
Internal failure of the 'E' position sensor inside the pedal
Pushed-back pin or damaged locking tab at the pedal connector
Open or shorted-to-ground 'E' signal wire
Open or shorted-to-ground 5V reference voltage to the 'E' sensor (some platforms use shared reference, others use separate)
Failed pedal assembly — sensors integrated, not separately serviceable
Recent interior or under-dash work that disturbed the pedal harness
Failed PCM input circuit for the 'E' sensor input (rare)

Symptoms

Check Engine Light on
'Reduced Engine Power' warning on the dash
Limp mode — throttle response is severely limited
Engine starts and idles normally
Throttle response is sluggish, capped, or non-existent past a small initial range
May feel like the pedal is partially disconnected
Pedal still moves freely with normal mechanical feel

Diagnostic steps

1.Pull all codes. Pairing matters: P2127 alone = 'E' circuit failure. P2127 + P2122 = both pedal sensors low (look for shared wiring fault). P2127 + P2138 = 'E' sensor confirmed-failed by correlation logic.
2.Locate the pedal assembly under the dash and inspect the harness for visible damage.
3.Disconnect the pedal connector and verify the wiring pinout for your platform — identify which pins belong to the 'E' circuit specifically.
4.With sensor disconnected, key on, check 5V reference at the 'E' reference pin (harness side). Confirm reference is present.
5.Check continuity from the 'E' ground pin (harness side) to chassis ground. Open ground here is a common cause.
6.Reconnect pedal. Use a scan tool to watch the 'E' sensor signal voltage as you press the pedal. Should sweep smoothly. Stuck-low confirms the failure.
7.If wiring tests good and 'E' signal is pegged low when connected, the pedal assembly is the failure point.
8.After replacement, perform the pedal relearn procedure.

Repair cost

$100 – $500

Same range as P2122 because the repair is typically the same component (pedal assembly) with the same labor. Low end is wiring repair when the diagnosis turns up a pinched wire or pushed-back pin — under $150. Mid-range $200-350 is pedal assembly replacement. Upper end is $400-500 for luxury platform assemblies. When P2122 and P2127 set together, the diagnostic time is slightly higher because the tech has to confirm whether the cause is shared wiring or a fully-failed pedal assembly.

Estimate your repair

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Open the Repair Cost Estimator with accelerator pedal position sensor replacement preselected. Adjust labor rate and vehicle category to fit your situation.

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DIY vs shop

This is an intermediate DIY job. It usually involves diagnostic steps, specialty parts, and some careful work in tight spaces. If you have the tools and a service manual or trustworthy video for your specific vehicle, it is achievable in a weekend. Otherwise, a competent independent shop will be faster.

Related codes

P2122 P2138 P2135 P0121 P0122 P0123P2128P2123