P3400 on Jeep
Cylinder Deactivation System Bank 1
P3400 on Jeep vehicles indicates cylinder deactivation system bank 1. Au7o has documented this code across 1 Jeep model — most commonly on Grand Cherokee. This code indicates the engine control module detected a fault in the cylinder deactivation (variable displacement) system on bank 1, the side of the engine containing cylinder number one. Cylinder deactivation closes the valves and cuts fuel to certain cylinders under light load to save fuel, using oil-pressure-operated control solenoids. When the system can't operate correctly, the module sets this code; you may notice reduced fuel economy, a slight performance change, or a warning light. The most common trigger is low oil level or poor oil pressure. Typical repair costs on Jeep range from $1,500 to $7,000, depending on the specific model and root cause.
Common Causes of P3400
- •Low engine oil level or low oil pressure
- •Clogged or dirty oil passages/lifters
- •Faulty active fuel management / cylinder deactivation solenoid
- •Failed deactivating lifter or collapsed lifter
- •Wiring or connector fault in the solenoid circuit
- •Sludge from missed oil changes
- •Faulty oil pressure sensor
P3400 on Jeep by Model
Jeep Grand Cherokee(1 issue)
- 5.7L HEMI MDS Lifter Collapse and Camshaft Lobe Wear ("HEMI Tick")2011-2021
On the 5.7L HEMI, the Multi-Displacement System (MDS) cylinder-deactivation roller lifters can collapse or seize, which in turn wipes the corresponding camshaft lobe. This produces the persistent hot-idle 'HEMI tick.' Once a lifter fails it spreads metal debris through the engine; FCA's own guidance is to replace the cam and lifters if no debris is found, or replace the engine if debris reaches the VVT solenoid and cam.
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What does P3400 mean on Jeep?▼
P3400 stands for "Cylinder Deactivation System Bank 1." This code indicates the engine control module detected a fault in the cylinder deactivation (variable displacement) system on bank 1, the side of the engine containing cylinder number one. Cylinder deactivation closes the valves and cuts fuel to certain cylinders under light load to save fuel, using oil-pressure-operated control solenoids. When the system can't operate correctly, the module sets this code; you may notice reduced fuel economy, a slight performance change, or a warning light. The most common trigger is low oil level or poor oil pressure. On Jeep specifically, this code is documented across 1 model.
What causes P3400 on Jeep vehicles?▼
Common causes on Jeep: Low engine oil level or low oil pressure, Clogged or dirty oil passages/lifters, Faulty active fuel management / cylinder deactivation solenoid, Failed deactivating lifter or collapsed lifter, Wiring or connector fault in the solenoid circuit. Specific causes vary by model and year — see the per-model sections below.
How much does it cost to fix P3400 on a Jeep?▼
Repair costs on Jeep range from $1,500 to $7,000, depending on the specific model and root cause.
Which Jeep models have P3400 documented?▼
Au7o has documented P3400 on 1 Jeep model: Grand Cherokee.