Bentley Bentayga P004100 After a Readiness Test? Run the Two Routines Back-to-Back

P004100 After Readiness? Keep The Sequence

Do not start by swapping oxygen sensors or wiring. Save the original P004100 and confirm whether it appeared after a readiness test with no drivability complaint. Bentley directs the workshop to run ODIS basic setting 3.7, the post-catalyst oxygen-sensor interchange test, and then immediately generate the readiness code. No ignition cycle, DTC deletion or unrelated test should interrupt those steps. If the code remains, the technician raises a DISS query and waits before further work.

If the uninterrupted ODIS sequence fails and Product Support later asks for signal evidence, a multimeter with oscilloscope capability can compare accessible related circuits through the approved wiring information. An AUTOOL DM303 fits that supporting role. DM303 can compare accessible oxygen-sensor or related circuit signals when Bentley’s wiring information and an approved back-probe method call for measurement; it cannot run ODIS basic setting 3.7, generate readiness, prevent an ignition-cycle error, identify a swapped signal from one trace alone or authorize sensor replacement.

Here, the order of two software routines is part of the diagnosis. Turning the ignition off, clearing the code or running a seemingly harmless test between them can create new readiness state and send the workshop toward the wrong conclusion.

Save the code before changing readiness state

Connect the diagnostic system and save the original event memory before clearing P004100. Record whether it is static or intermittent, the mileage, the readiness-test history and any accompanying faults. Ask the crucial question: did the MIL appear while someone was trying to generate an emissions-readiness result? If the engine actually runs poorly, smells rich, misfires or has other oxygen-sensor circuit codes, preserve those differences. Bentley’s measure begins with either no DTCs or no engine-operation issues; it is not a universal cure for every oxygen-sensor complaint.

Ask what happened immediately before the MIL

Reconstruct the minutes before the warning. Note whether the engine was already warm, which test application was open, whether codes were deleted, whether the ignition was cycled and whether the routine was stopped. A generic note such as ‘failed inspection’ loses the most useful clue. The code description sounds as if two physical connectors must be crossed, but Bentley’s production-change note says the applicable ODIS routine will be updated to conduct an additional basic setting automatically. That makes test sequence the first suspect, not proof of crossed harnesses.

Confirm the Bentayga V8 scope

TPI 2065664/6 lists specified Bentayga V8 Kovomo sales types across several model years, including later 2026–2027 variants. Confirm the VIN and sales type in current Bentley information. Do not apply the process to another Volkswagen Group V8 merely because the code text matches. Check whether the vehicle has already received the updated diagnostic routine and whether exhaust or oxygen-sensor work was recently completed. A truly swapped connector after repair is still possible; the bulletin’s procedure should not erase credible physical-history evidence.

Rule out an active running problem first

Before entering the special routine, confirm there is no active drivability issue and save an online log showing the starting fault state. Inspect only what can be checked without disturbing the readiness state: obvious harness damage, disconnected sensors or an unsafe exhaust condition. Do not perform a road test, delete faults or toggle the ignition just to make the screen look clean. If another active DTC changes the meaning of the test, follow Bentley’s guided path. The goal is to begin the two-step sequence from a documented, valid state.

State	Next action
P004100 appeared after readiness, no running complaint	Preserve the log and run the two routines continuously
Other active running or circuit faults	Follow guided diagnosis for those faults first
Code gone after basic setting + immediate readiness	Save the result; allow remaining monitors to complete normally
P004100 remains after exact sequence	Raise DISS and wait before further work

Run basic setting 3.7 in ODIS

In ODIS, run the engine basic-setting routine and select option 3.7, ‘Test for oxygen sensor interchange after catalytic converter.’ Follow every on-screen instruction to completion. This is a software-controlled comparison of the downstream sensors, not an invitation to swap physical parts as a test. Keep approved voltage support connected and do not begin unrelated measurements. Save the ODIS log and completion result. If the routine cannot start or aborts, document the message rather than improvising ignition cycles that alter the readiness condition.

Generate readiness without an interruption

Immediately after basic setting 3.7, remain in the defined state. From Engine Control Module 1 guided functions, select ‘Generate readiness code,’ execute it and follow the prompts through completion. Bentley specifically says not to introduce ignition cycles, DTC deletion or other tests during these steps because those actions can set readiness and log unrelated faults. ‘Immediately’ is the important word: this is one continuous procedure with two named routines, not two jobs that can be split across a lunch break or technician handoff.

Do not demand every byte be zero

Not every readiness byte needs to be zero at the end of this workshop procedure; Bentley notes that remaining bytes can set during normal drive cycles. Read the actual ODIS result rather than chasing a visually perfect screen. Save which monitors are complete, which remain pending and whether P004100 returns. An incomplete monitor is not the same thing as a sensor interchange fault. If an inspection deadline is involved, explain that a normal drive cycle may still be needed instead of clearing memory again and resetting all monitors.

Escalate through DISS if P004100 remains

If P004100 remains after the exact uninterrupted process, stop. Bentley directs the operative to raise a DISS query and wait for Product Support before further work. Attach the original event memory, online log, ODIS routine logs, readiness state, software versions and relevant repair history. Only then should targeted signal comparison or connector inspection be performed if requested. Replacing both downstream sensors, swapping connectors experimentally or repeating readiness routines can add faults and obscure the original problem. Escalation is an active diagnostic step when the manufacturer is revising the routine.

This is a rare case where good workmanship looks like restraint and timing. Save the original event, confirm the Bentayga scope, run basic setting 3.7, and generate readiness immediately without cycling the ignition or clearing anything in between. If the code remains, stop and send the complete log to DISS. Verify the outcome from the saved routine log and final fault state, not from an assumption that the warning has gone away. That protects the owner from paying for oxygen sensors when the missing ingredient may simply be the correct ODIS sequence.

Official references

• Bentley TPI 2065664/6—P004100 O2 Signals Swapped
• NHTSA Recall Lookup