Parts for your 2004 Toyota Mark x-Camshaft sensor

2004 Toyota Mark X camshaft sensor — what it does, where it lives, and when to replace it

Yes, the 2004 Toyota Mark X uses camshaft position sensors. Technical references including the Toyota Repair Manual for the GRX120/121 series (4GR-FSE/3GR-FSE engines), the Toyota Electronic Parts Catalogue, and factory DTC charts confirm dual camshaft position sensors are fitted—one on each cylinder bank. These sources list diagnostic procedures and fault codes such as P0340/P0345 (Camshaft Position Sensor “A” Circuit Bank 1/2), showing the sensors are integral to Dual VVT-i control, sequential fuel injection, and ignition timing on this model.

On the Mark X, the camshaft sensor tells the engine control module exactly where the cam is in its rotation. That timing info is crucial for precise fuel delivery and spark, and it lets the ECU actively phase the cams through Dual VVT-i for better torque, fuel economy and emissions. If a sensor starts to play up, the ECU can lose sync, dial back performance, or default to a safe strategy to keep the engine running—though you’ll feel it.

Typical signs a camshaft sensor needs attention include:

• Hard starting, extended cranking, or intermittent stalling under the bonnet
• Rough idle, flat spots, or misfires, especially when warm
• Higher fuel use and a noticeable drop in pull
• Check Engine Light with codes like P0340/P0345 or cam/crank correlation faults

There’s no scheduled replacement interval—these solid-state sensors aren’t a routine wear item. As part of servicing, it’s smart to inspect the connectors on both cylinder heads, check the harness routing for rubbing or heat damage, and look for oil seepage past the O-ring at the sensor body. A quick scan for stored or pending codes during regular maintenance can catch an issue early.

Replacement is straightforward: disconnect the battery, unplug the connector, remove the retaining bolt, and ease the sensor out. Fit a new O-ring, lightly oil it, seat the new sensor squarely, and snug the bolt without over-tightening. Clear fault codes and road-test, the ECU will typically relearn without special procedures. On V6 models, label each bank’s connector if removing more than one item around the timing cover to avoid mix-ups.

If faults persist after fitting a quality sensor, consider a deeper look: wiring integrity, oil sludge affecting VVT operation, or timing chain stretch can all mimic a bad sensor on GR-series engines. A proper scan-tool data check of cam/crank correlation under load helps pinpoint the real culprit.

Popular questions

How many camshaft sensors does a 2004 Mark X have?

The GR-series V6 in the Mark X uses two camshaft position sensors—one on Bank 1 and one on Bank 2. They provide the ECU with accurate phase information to run Dual VVT-i and sequential injection.

Is it safe to drive with a faulty camshaft sensor?

It may start and run, but performance can be reduced and stalling is possible. Short trips to a workshop are usually fine, but it’s best not to keep driving as prolonged faults can mask timing or VVT issues that deserve quick attention.

Can timing chain stretch trigger cam sensor fault codes?

Yes. On GR engines, excessive chain wear or a jumped tooth can cause cam/crank correlation codes that look like a sensor problem. If a new sensor doesn’t fix it, have the timing and VVT operation checked with a scan tool and mechanical inspection.