Mercedes GLS450 Rough Idle and P035113: Cylinder 1 Ignition Coil Replaced

A Mercedes-Benz GLS450 with an M276 V6 arrived; its model year, chassis code, and mileage were not reported. The driver had a yellow engine warning, a hard uneven idle, and a noticeable stumble when accelerating. The source case confirmed an electrical open-circuit failure in the cylinder 1 ignition coil actuator, replaced that one coil, cleared the codes, and reported a smooth idle with the warning no longer illuminated.

Case at a glance

The yellow lamp came with a missing beat

This was not a warning-light-only visit. The source describes an engine that shook strongly at idle, sounded uneven at the tailpipe, and stumbled when the driver asked for acceleration. Those details matter because they give the scan result something concrete to explain: one cylinder was apparently no longer contributing normally.

The warning lamp alone could not name a failed part. Rough running can involve ignition, fueling, air, mechanical sealing, wiring, or control. The first useful move was to preserve the complaint and read the stored faults.

P035113 narrowed the search to one ignition channel

The scan screen displayed P035113, described here as an electrical fault or open circuit in the cylinder 1 ignition-coil actuator. The source also reports scan data showing that cylinder’s ignition operation had stopped. The rough idle now had a cylinder-specific electrical direction.

A circuit code can be associated with the coil, connector, wiring, supply, or control side. The source identifies the coil as failed but publishes no resistance, waveform, swap, harness-continuity, or pin-defect result. Those tests should not be invented.

The physical handoff was from code to cylinder 1

The video next moves from the tablet to the M276 engine bay and points out the cylinder 1 coil and connector. This is the diagnostic turning point readers can actually follow: the scan supplied a cylinder and circuit, then the technician located the matching component before defining the repair.

The evidence does not mean every P035113 requires a coil. This GLS450’s source diagnosis and same-condition result support that decision; another car could retain the same circuit wording with a connector or harness fault.

Do not unplug or probe a coil with the engine running. Connector, supply, control-wire, or high-voltage testing requires exact-vehicle wiring information and a qualified procedure; this case supplies no pin assignments or values.

One coil defined the repair boundary

The actual parts decision was small: replace the cylinder 1 ignition coil. No other coil, spark plug, connector, harness, or engine-control repair was reported. The source’s general plug-inspection suggestion is not work performed here.

At a broad level, access was opened, the affected coil was removed, the replacement was installed, and the connection was restored. Exact access order, part number, torque, pinout, and electrical values are not reported and must come from exact-vehicle information.

The decision joins the cylinder-specific circuit fault, reported stopped ignition operation, part-level diagnosis, and result after replacing only that coil. It is not a recommendation for bank-wide replacement.

Code clearing reset the question; it did not answer it

After installation, the stored faults were cleared. The tablet confirms completion, and the source reports that the system self-check passed. Clearing reset the warning state for a fresh observation; it could not alone prove that the open circuit or rough idle was gone.

The engine then had to revisit the driver’s complaint. A returning lamp or continued miss would leave the diagnosis unresolved regardless of the clear-code message.

The final idle check challenged the original complaint

The final cabin view shows the engine running with the yellow engine warning no longer illuminated. The source also reports restored six-cylinder smoothness. This staged verification challenges both the warning state and the original shake.

No repeat full-system scan, road-test distance, equivalent acceleration retest, cold-soak restart, or later follow-up is reported. The immediate idle and lamp result supports the repair without becoming a durability claim.

A first-check order for another rough-running GLS

For a similar complaint, first reproduce and describe the running problem: lamp state, idle quality, sound, and the condition that produces the stumble. Next, scan before clearing anything and record whether the fault is cylinder-specific, circuit-specific, or combustion-related. Then inspect the named coil connection and wiring, and use appropriate electrical or comparison tests to distinguish the component from its circuit before authorizing a part. After repair, restore connections, clear faults only when appropriate, rescan, and challenge the original symptom at idle and under the condition that first produced it.

This GLS450’s answer was one confirmed cylinder 1 ignition-coil failure followed by a successful immediate idle and warning-lamp recheck. Do not copy that part decision to another vehicle unless its own circuit evidence points to the same fault.