Quick answer
The powertrain control module (PCM) uses crankshaft-position (CKP) and camshaft-position (CMP) signals to identify engine speed and position, sequence ignition and fuel injection, monitor the crank-to-cam relationship, and verify variable cam timing. P0340 is primarily a CMP signal or circuit category. P0016 means the PCM can recognize the position signals but sees their relationship outside the expected range. Neither code, by itself, proves that a sensor or timing chain has failed.
Applicability and service-information boundary
This overview applies to the 2019-2025 Ram 2500HD 6.4 HEMI Gas configuration. Authorized vehicle records confirm a Ram 2500 Truck 4WD application with the 6.4-liter V8 in every model year from 2019 through 2025, and Ram model-year material identifies the engine family as the 6.4L HEMI V8.
The detailed operating and diagnostic information reviewed for this overview comes from the exact 2025 application. Calibration, wiring, circuit identifiers, scan-tool functions, sensor design, target patterns, component access, specifications, and repair procedures can change by year and equipment. Use current service information for the exact truck whenever a test requires a value, connector, command, special tool, relearn, or removal procedure.
What the timing and position system does
Mechanical timing establishes the physical relationship between the crankshaft, camshaft, pistons, and valves. The electronic position system tells the PCM where those rotating parts are. Variable cam timing (VCT) then changes camshaft position within a controlled range to support performance, emissions, and combustion stability.
These layers work together, but they answer different diagnostic questions:
- The timing chain, sprockets, guides, tensioner, cam phaser, and related hardware establish and maintain the mechanical relationship.
- The CKP sensor reads a crankshaft target and provides the PCM with engine-speed and crank-position information.
- The CMP sensor reads a camshaft tone wheel and provides a digital pattern that identifies camshaft position within the engine cycle.
- The VCT oil-control valve and cam phaser use controlled engine-oil flow to move cam timing when commanded.
- The PCM compares CKP and CMP patterns, monitors commanded cam movement, and stores learned crank/cam information used during later operation.
A DTC identifies the evidence the PCM could not validate. It does not identify the failed part without further testing.
How CKP and CMP signals create synchronization
The CKP signal is the PCM's detailed reference for crankshaft motion. The CMP signal tells the PCM which part of the four-stroke cycle is occurring. When both patterns are recognized, the PCM can synchronize ignition and injection events and judge whether the camshaft is positioned correctly relative to the crankshaft.
The CMP sensor in the reviewed application is a digital sensing device supplied with a reference and ground by the PCM. As the camshaft tone wheel passes the sensor, the output switches to create a pulse pattern. The PCM decodes that pattern rather than relying on a single static voltage.
This matters during diagnosis. A scan tool may show a code, but it cannot prove every pulse is clean. A scope can reveal dropout, distortion, incorrect spacing, or a relationship that changes with temperature, vibration, or engine speed. Circuit integrity, signal quality, target condition, and mechanical relationship are separate layers.
How correlation and VCT fit together
P0016 is evaluated only after the PCM has recognized and locked the relevant CKP and CMP positions. It then compares their angular relationship with the learned expectation. Because both signals can be present while their relationship is wrong, a correlation fault is not simply another version of a missing-signal code.
The cam phaser adds a controlled moving element. The PCM commands an oil-control valve, engine oil moves the phaser, and CMP feedback shows whether the camshaft reached the expected position. Low oil level, unsuitable or contaminated oil, aeration, restricted flow, insufficient pressure, a sticking oil-control valve, or a phaser problem can affect that response even when the electrical position signals are present.
Mechanical timing can also shift because of chain or sprocket alignment, a damaged guide or tensioner, a phaser or target-wheel problem, or incorrect assembly after service. The correct diagnostic order is therefore to prove the signals and basic oil/VCT conditions before opening the timing drive.
What P0016 and P0340 are telling you
| DTC | Diagnostic category | What it directs you to prove |
|---|---|---|
| P0016 | Crankshaft/camshaft correlation or timing misalignment | Whether recognized CKP and CMP patterns remain in the expected relationship, then whether oil condition and pressure, VCT control, phaser/target condition, or mechanical timing has shifted |
| P0340 | CMP signal or circuit fault | Whether reference, ground, signal, connector, harness, sensor mounting, sensor output, tone wheel, and PCM recognition are sound before any component is condemned |
P0340 does not automatically mean “replace the camshaft sensor.” P0016 does not automatically mean “replace the timing chain.” Treat the code as a starting classification and make the next test prove one branch.
What the driver or technician may notice
Possible observations include:
- a malfunction indicator lamp with little immediate change in drivability;
- extended cranking while the PCM establishes synchronization from the remaining position information;
- rough operation, reduced response, or a related misfire concern when timing or VCT response is affected;
- a code that appears after sensor, valvetrain, flywheel, timing-drive, or control-module work;
- an intermittent code that changes with heat, vibration, harness position, oil condition, or engine speed;
- related reference-circuit, VCT, oil-pressure, position-signal, or misfire DTCs.
Symptoms do not identify the failed branch. Preserve the full scan and operating record before clearing codes.
Common failure categories
CMP circuit, connector, or signal fault
An open, short, excessive resistance, poor terminal fit, corrosion, water intrusion, damaged lock, harness rub, or intermittent connection can remove or distort the CMP signal. A shared reference problem can affect more than one sensor and should be handled before replacing the CMP sensor.
Inspect recent service areas and harness routing. Use terminal-safe tests and the exact wiring information. Avoid forcing probes into PCM terminals; connector damage can create the fault you are trying to diagnose.
Sensor mounting, debris, or target-wheel fault
A sensor that is loose, incorrectly seated, damaged, or separated from its target by debris may produce an unreliable pattern. A loose, damaged, or misaligned tone wheel can create a believable electrical pulse train with incorrect timing.
Inspect mounting and target condition only with the approved access and rotation procedure. A new sensor cannot correct a damaged target or an installation problem.
Oil supply or VCT control fault
The cam phaser depends on controlled engine-oil flow. Low level, unsuitable viscosity, contamination, aeration, an incorrect filter, restricted flow, or insufficient pressure can prevent the phaser from moving or returning correctly. The oil-control valve can also stick or fail to respond.
Verify oil condition and pressure using the current procedure before condemning a phaser or opening the timing drive. Separate the electrical command, valve operation, oil supply, and mechanical response.
Mechanical timing, phaser, guide, or tensioner fault
Chain or sprocket misalignment, a worn or damaged chain, a broken guide or tensioner, a phaser problem, or a shifted target can change the relationship between stable CKP and CMP signals.
This branch becomes credible when the signals are present and stable, related electrical faults are resolved, oil/VCT conditions are known, and the correlation evidence remains. Do not begin with engine disassembly merely because P0016 is stored.
Intermittent or recent-service fault
Heat, vibration, engine movement, oil temperature, harness position, or a connector disturbed during service can make the concern disappear in the bay. Incorrect timing assembly, sensor installation, or a skipped relearn can also create a post-repair code.
Use the original failure record and a controlled harness or operating-condition test. If the fault is currently absent, do not manufacture a parts replacement without repeatable evidence.
PCM or software is suspected too early
Control-module failure is possible but belongs late in the diagnostic tree. Applicable service information and software updates, power and ground integrity, circuits, terminals, sensors, targets, oil/VCT response, and mechanical timing must be evaluated first.
Replacing or programming a PCM before proving those inputs can add a relearn or configuration problem without fixing the original fault.
A practical system-first diagnostic strategy
Step 1: Confirm applicability and preserve evidence
Verify the VIN, model year, 6.4-liter engine configuration, calibration, and current service information. Save the complete module scan, active/pending/stored DTCs, failure records, CKP/CMP synchronization or activity, commanded and actual cam data, oil information, and recent repair history before clearing anything.
Step 2: Classify the primary fault
Separate a missing or unstable CMP signal from a crank/cam correlation fault. P0340 directs you toward the CMP circuit and pattern. P0016 requires recognized position information and directs you toward relationship, oil/VCT, target, and mechanical-timing evidence.
Step 3: Resolve shared and prerequisite faults first
Follow the exact code-priority instructions. Diagnose shared reference, power, ground, communication, oil-pressure, or related VCT faults before relying on a correlation test. Multiple codes can be consequences of one shared problem.
Step 4: Check oil condition and recent service history
Verify the specified oil level, condition, viscosity, filter application, and pressure when the directed path requires it. Ask whether the concern began after oil service, CMP or CKP work, flywheel work, valvetrain repair, timing-system work, or PCM programming.
Step 5: Prove signal presence and quality
Use scan data to see whether the PCM recognizes CKP and CMP activity, then use the applicable circuit tests and waveform inspection when needed. A present signal is not automatically a correct signal. Look for dropout, noise, poor amplitude or switching, timing drift, and response to controlled harness movement.
Step 6: Inspect the connector, mounting, and target
Check locks, seals, terminal fit, moisture, corrosion, harness damage, sensor seating, mounting-surface condition, debris, and visible target damage. Restore anything disturbed during inspection and use the specified rotation and access method.
Step 7: Separate VCT command from VCT response
If the signals are credible but correlation remains wrong, verify the oil-control side in the service-information order. A valid electrical command with incorrect cam movement points toward oil supply, valve movement, phaser operation, or mechanical timing rather than the sensor circuit alone.
Step 8: Inspect mechanical timing only when supported
Evaluate chain and sprocket alignment, guide and tensioner condition, phaser/target condition, and related mechanical fitment only after the earlier evidence supports this branch. Use the exact alignment tools, procedures, fasteners, sealing instructions, and torque specifications for the truck.
Step 9: Perform required learning and verification
The reviewed procedures require a Cam/Crank Relearn after specified CKP/CMP, flywheel, valvetrain, timing-chain, or gear work. Follow the exact scan-tool routine and prerequisites. Do not repeatedly command a relearn while a signal, oil-pressure, or mechanical fault remains.
Reproduce the original operating conditions, confirm stable synchronization and cam response, rerun the relevant monitor, and verify that no pending or confirmed DTC returns. Clearing the MIL without restoring the learned relationship and rerunning the monitor is not a verified repair.
Safety before testing or relearning
Position-signal tests and relearn procedures may require cranking, a running engine, or controlled changes in engine speed. Work in a ventilated area, set the parking brake, secure the truck against movement, and keep hands, clothing, tools, leads, and loose objects away from belts, pulleys, fans, and hot exhaust parts. Do not stand in front of or behind an unsecured truck during a commanded procedure.
Follow the exact power-down and battery procedures before disconnecting sensors or PCM connectors. Engine oil and components may be hot. If mechanical timing work is required, use the specified support, holding, alignment, fastener, sealing, lubrication, and verification procedures. Stop a relearn or functional test if the engine behaves abnormally or a prerequisite is not satisfied.
Match the repair to the proven failure
The supported repair may involve terminal or wiring repair, connector service, correcting sensor installation, removing debris, replacing a proved CMP sensor, correcting a tone wheel, restoring correct oil and filter condition, repairing an oil-pressure problem, servicing the VCT oil-control valve or phaser, repairing the chain/guide/tensioner system, correcting mechanical alignment, or completing the required relearn. PCM work belongs at the end of the applicable diagnostic path.
Mechanical timing repairs are precision work. Current service information for the exact truck controls alignment, holding, one-time-use parts, torque, sealing, oil-system preparation, programming, learning, and final verification.
Final takeaway
On the 2019-2025 Ram 2500HD 6.4 HEMI Gas, timing diagnosis is a comparison among mechanical alignment, CKP and CMP signal integrity, oil-supported VCT response, learned crank/cam relationship, and PCM interpretation. P0340 asks whether the CMP circuit and pattern are trustworthy. P0016 asks whether trustworthy position patterns remain correctly related.
Preserve the evidence, classify the DTC, resolve shared faults, prove the signals, verify oil and VCT response, and inspect mechanical timing only when the evidence points there. Complete the required relearn and rerun the monitor before calling the repair finished. The linked STEP guides provide model-specific educational paths; current service information for the exact truck controls specifications, commands, connectors, component locations, disassembly, and verification.
