🚨 Diagnostic Profile
Vehicle Make: Chrysler
Description: IC Cylinder 8 Not Toggling After Enable. This indicates the Cylinder 8 deactivation (Multi-Displacement System) solenoid or its control circuit is not responding correctly after the engine control module (ECM/PCM) commands cylinder reactivation. The fault is typically associated with Chrysler/Dodge/Jeep V8 engines (5.7L HEMI, 6.4L HEMI) equipped with Multi-Displacement System (MDS) or Fuel Management System (FMS) technology.
🚨 Repair Difficulty Tier
Tier: [Intermediate]
Diagnosis requires scan tool access, live data monitoring, and electrical circuit testing. Physical repair ranges from simple (solenoid replacement) to moderate (lifter or lifter-oil-gallery service) depending on root cause.
🛠️ Resolution Steps
Step 1: Preliminary Inspection
- Verify engine oil level, condition, and correct viscosity specification for the vehicle (MDS systems are highly sensitive to low oil volume and incorrect viscosity, which directly affects solenoid oil-control actuation).
- Inspect the engine oil pressure and confirm it meets factory specifications at operating temperature using a mechanical gauge, not just the dash gauge/sender signal.
- Scan all modules for active and stored DTCs, including misfire codes, cylinder-specific MDS fault codes, and any correlating oil pressure or oil control valve codes.
- Inspect the Cylinder 8 deactivation solenoid connector (located within the MDS solenoid pack mounted in the lifter valley beneath the intake manifold) for corrosion, bent pins, moisture intrusion, or a loose/unseated connector lock.
- Inspect the Cylinder 8 solenoid harness for chafing, heat damage, or pinched routing along the intake manifold valley and harness pass-through grommets.
- Check for oil leaks or oil contamination at the valve cover, lifter valley cover gasket, and MDS solenoid pack mounting surface, as leaks here can cause oil pressure loss to the affected solenoid circuit.
Step 2: Diagnostic Verification
- Monitor live data for the MDS/FMS deactivation command state and actual lifter/cylinder status while commanding enable/disable through a bidirectional scan tool; compare commanded state to actual feedback state for Cylinder 8.
- Measure solenoid supply (reference) voltage at the connector under commanded load using a digital multimeter against a known good chassis/engine ground; confirm voltage is present and stable (near system battery voltage) when the PCM commands the solenoid on.
- Measure solenoid control circuit resistance and check continuity end-to-end per factory service information; compare the reading against the OEM-specified acceptable range rather than assuming a fixed value, as MDS solenoid resistance specs vary by engine family and model year.
- Check for a short to ground or short to voltage on the control circuit by probing the harness with the connector disconnected and key off, then verifying no continuity to ground or battery voltage is present on the signal wire.
- Perform a solenoid activation test (listen/feel for an audible click or confirm via scan tool actuator test) to verify mechanical actuation of the oil control solenoid.
- Verify PCM/ECM command output for Cylinder 8 using a bidirectional scan tool actuator test or a lab scope on the control circuit; confirm the module is pulsing/grounding the circuit as commanded with no signal dropout.
- Check the Cylinder 8 lifter or deactivation mechanism for mechanical sticking by reviewing misfire counters, cylinder balance/power balance test results, and relative compression data; a mechanically stuck lifter will often show as an MDS fault even with a fully functional solenoid and circuit.
Step 3: Resolution & Reset Process
- Replace the Cylinder 8 deactivation solenoid (as part of the MDS solenoid pack assembly) if it fails resistance, voltage, or actuation tests.
- Repair any harness damage, corrosion, or high-resistance connections in the control circuit using OEM-approved splice/repair techniques and weatherproof connectors; do not solder-only repairs in high-vibration engine valley locations without proper strain relief.
- If the lifter or deactivation mechanism is mechanically sticking, perform lifter valley service per the applicable Mopar Techline service procedure for MDS lifter/collapsed lifter concerns, which typically includes lifter valley cover removal, lifter inspection/replacement, and lifter bore/oil gallery cleaning.
- Correct any oil-pressure, oil-dilution, or oil-quality issue (including verifying correct oil type and change interval) before further diagnosis, as this is a leading root cause of MDS toggle faults.
- Clear all DTCs using the scan tool and perform any required PCM relearn, oil life reset, or MDS/FMS system self-test/verification drive cycle per factory procedure.
- Road test under varied load and RPM conditions to allow the PCM to command MDS activation/deactivation naturally, and confirm Cylinder 8 toggles correctly in live data with no returning codes.
📦 Parts, Labor, and Budget Estimates
Required Components/Software:
- OEM Mopar MDS/FMS solenoid pack assembly (VIN-specific; verify exact Mopar part number through dealer parts catalog or OEM parts lookup for the specific engine code).
- Solenoid connector pigtail or harness repair kit (if corrosion/damage confirmed) — OEM Mopar harness repair connector kit.
- Engine oil and filter meeting Chrysler/Mopar MS-6395 specification (typically 5W-20 or 0W-40 depending on engine and model year — confirm via owner’s manual/fluid cap).
- Lifter valley cover gasket set and MDS lifters (if mechanical sticking confirmed) — OEM Mopar lifter kit specific to engine displacement.
- OEM-level bidirectional scan tool (e.g., Mopar wiTECH/StarMOBILE or equivalent aftermarket tool with Chrysler bidirectional actuator test capability) and current software/subscription access.
Average Component Price:
- MDS Solenoid pack assembly: approximately $150–$350 (part only, varies by engine/model year)
- Harness/connector repair kit: approximately $40–$120
- Engine oil and filter service: approximately $60–$120
- Lifter valley service parts (gasket, lifters if needed): approximately $300–$900 (parts only, lifters are often sold as a full set)
- wiTECH/dealer-level diagnostic software access (per session/day, if required): approximately $30–$70
Estimated Labor Hours:
- Diagnostic verification (scan, live data, circuit testing): 1.0–2.0 hours
- Solenoid pack replacement (intake manifold removal, lifter valley cover access required): 2.5–4.0 hours
- Harness or connector repair: 0.5–1.5 hours
- Lifter/mechanical valley service (full lifter valley teardown, lifter replacement): 4.0–7.0 hours
- Post-repair verification, DTC clear, and MDS system reset/road test: 0.5–1.0 hour