P0340 on 2012-2016 GMC Sierra 2500: Camshaft Position Sensor Circuit Fault Causes & Fixes

What's Unique About the 2012-2016 Gmc SIERRA 2500

For this generation of Sierra, GM has issued several Technical Service Bulletins (TSBs) related to P0340, indicating a known pattern of issues. TSB #PIP5099A specifically points to a batch of faulty sensors in 2012 models built in September or October. Other TSBs like #PIP5335C and #PIP5198 (for 2015 Duramax) show that GM was actively tracking intermittent signal issues, often related to wiring and connections. On the 6.0L V8, the sensor is located behind the water pump, making replacement more involved. 🎬 See this step-by-step replacement guide for the 6.0L V8. On the 6.6L Duramax, the sensor is on the front of the engine, but wiring can chafe on the EGR valve gasket. These factors suggest that while the sensor itself is a common failure point, a thorough, engine-specific inspection of the wiring is critical before replacing parts.

Diagnostic Flowchart

Tap your situation to follow the diagnostic path that matches what you're seeing on this vehicle.

Generation note: This range covers two generations of the Sierra 2500: the second generation (GMT900, 2012-2014) and the third generation (K2XX, 2015-2016). The primary engines, the 6.0L Vortec V8 gas and 6.6L Duramax V8 diesel, were carried over between generations. The TSBs provided cover years in both generations, suggesting the P0340 issue is related to the powertrain components rather than a specific chassis design. For the 6.0L gas engine, the sensor is located behind the water pump, while on the 6.6L Duramax, it is on the front of the engine near the harmonic balancer.

Symptoms You May Notice

• Check Engine Light is on
• Engine is hard to start or has an extended crank time
🎬 Watch: Troubleshooting a long crank time and P0340 code.
• Engine stalls unexpectedly
• Rough idle or misfiring
• Noticeable loss of power and poor acceleration
• Engine may not start at all
• Tachometer needle jumping erratically (on some models)

Most Likely Causes

1. Faulty Camshaft Position Sensor 🔴 High Probability Heat and oil leaks in the engine bay can cause the sensor to fail over time. TSB #PIP5099A also notes a potentially bad batch of sensors for specific 2012 models built in September or October.
   How to confirm: After verifying wiring is intact, test the sensor's output with a multimeter or oscilloscope. The simplest confirmation is often replacing the sensor, as it's a relatively inexpensive part.
   Typical fix: Replace the camshaft position sensor.
   Est. part cost: $25-$110
2. Wiring Harness or Connector Issue 🔴 High Probability The wiring harness can become damaged, corroded, or loose. Specific chafe points are known to exist, such as against power steering lines or the A/C compressor. For 2015 Duramax models, TSB #PIP5198 points to the harness chafing on the EGR valve metal gasket. Rodent damage to farm or work trucks is also a documented possibility.
   How to confirm: Visually inspect the entire circuit from the sensor to the PCM for any signs of chafing, breaks, melting, or corrosion at the connectors. Wiggling the connector while observing a live data stream or oscilloscope can reveal a poor connection. Check for 5V reference, ground, and signal continuity using a multimeter.
   Typical fix: Repair the damaged section of wiring with solder and heat shrink, or replace the connector pigtail.
   Est. part cost: $10-$100
3. Weak Battery or Charging System Issue ⚪ Low Probability Low voltage during cranking can sometimes cause erratic sensor readings, triggering a fault code. A faulty alternator producing excessive AC ripple (electrical noise) can also interfere with the cam sensor signal.
   How to confirm: Test the battery and alternator to ensure they are functioning correctly. A simple voltage test during cranking can reveal a weak battery. An oscilloscope can be used to check for AC ripple from the alternator.
   Typical fix: Charge or replace the battery, or repair/replace the alternator.
   Est. part cost: $150-$600

Rare But Worth Checking

• Timing Chain/Belt Issue: A stretched timing chain can cause the camshaft and crankshaft signals to be out of sync, which may trigger a P0340 or related performance code (P0341). This is a more serious mechanical issue and is less common than sensor or wiring faults.
• Faulty Powertrain Control Module (PCM): This is very rare and should only be considered after all other possibilities (sensor, wiring, mechanical) have been exhaustively ruled out.
• Damaged Reluctor Wheel: The reluctor wheel on the camshaft, which the sensor reads, can be damaged or have missing teeth, leading to an inconsistent signal. This is an uncommon mechanical failure.

Diagnosis Steps

1. Read the trouble codes with an OBD-II scanner and note any other codes present, especially P0341, P0335, or P0641.
2. Perform a thorough visual inspection of the camshaft position sensor, its connector, and the entire wiring harness. On 6.0L engines, check for chafing near power steering lines. On 6.6L Duramax engines, specifically inspect the harness near the EGR valve for damage as noted in TSB #PIP5198.
3. Check for rodent damage, which is common on work trucks.
4. With the key on, engine off, use a multimeter to check for a 5-volt reference and a good ground at the sensor connector.
5. If power and ground are good, use a scan tool to view live data for a 'CMP Counter' or 'Cam Signal Present' PID while cranking the engine. An oscilloscope is the best tool to check for a proper square wave signal from the sensor.
🎬 Watch: How to diagnose and fix the P0340 code.
6. If the signal is absent or erratic (shows dropouts when wiggling wires), and the wiring is confirmed to be good, the camshaft position sensor is likely faulty.
7. If you have a 2012 model built in Sept/Oct, and other diagnostics are inconclusive, replace the sensor as per TSB #PIP5099A.
8. After repair, clear the codes and perform a test drive to ensure the issue is resolved.

Parts You'll Likely Need

• Camshaft Position Sensor (OEM #ACDelco 12674720 (for 6.0L V8) or ACDelco 12634313 (for 6.6L V8)) — This is the most common component to fail and trigger a P0340 code.
  Trusted brands: ACDelco, Delphi, Standard Motor Products
  OEM price range: $45-$110
  Aftermarket price range: $25-$75
• Camshaft Position Sensor Connector Pigtail — The connector itself can become corroded, or the locking tab can break, causing a poor connection. A pigtail is needed if the connector or wires immediately attached to it are damaged.
  Trusted brands: ACDelco, Dorman
  OEM price range: $20-$40
  Aftermarket price range: $10-$25

Related Codes That Often Appear With This One

• P0341 — P0341 indicates a 'Range/Performance' issue with the same sensor circuit. TSB #PIP5335C mentions P0340 and P0341 occurring together, suggesting an intermittent or unstable signal.
• P0335 — This code is for the Crankshaft Position Sensor. TSB #PIE0416A groups P0335 and P0340, indicating GM was tracking related cam/crank signal issues that could occur under similar conditions.
• P0641 — This code indicates an issue with the '5V Reference 1 Circuit'. Since the camshaft position sensor uses a 5V reference from the PCM, a fault in this circuit can trigger P0340 along with other sensor codes. TSB #PIP5198 for the 2015 Duramax lists P0641 and P0340 together as potential codes from a chafed harness.

Technical Service Bulletins (TSBs) & Recalls

• PIE0416A
• PIP5335C
• PIP5099A
• PIP5198

Platform-Specific Known Issues

• Bulletin #PIP5099A: For 2012-2013 models with various V8 engines (including the 6.0L) built in September or October 2012, this TSB advises replacing the cam position sensor if standard diagnostics do not resolve an intermittent P0340 code.
• Bulletin #PIP5335C: This TSB addresses P0340 and P0341 codes, instructing technicians to follow standard service information for diagnosis, implying a focus on foundational checks like wiring and connections.
• Bulletin #PIE0416A: This bulletin notes that GM has concluded its data collection on field incidents related to codes P0335, P0340, and P0365, indicating these were known and monitored issues.
• Bulletin #PIP5198: For 2015 models with the 6.6L Duramax (LML) engine, this bulletin warns of the engine wiring harness chafing on a tab of the EGR valve metal gasket, which can cause multiple DTCs, including P0340.

Mechanic-Grade Diagnostic Values

• Camshaft Position Sensor 5V Reference Circuit — expected: 4.8-5.2 volts with key on, engine off, measured between the 5V reference pin and ground.. Failure: Voltage below 4.8V suggests a short to ground or an open circuit; voltage above 5.2V suggests a short to voltage.
• Camshaft Position Sensor Ground Circuit Resistance — expected: Less than 1.0 to 5.0 ohms between the sensor's ground pin and a known good chassis ground.. Failure: Resistance higher than the specified value indicates a poor ground connection, which can cause erratic signals.
• Camshaft Position Sensor Signal (Manual Test) — expected: Voltage should toggle between ~5V (or 4.8V) and 0V when a metal object (like a socket) is passed in front of the sensor tip.. Failure: No change in voltage indicates a dead or non-responsive sensor.
• 6.0L Vortec Cam Sensor Wire Colors — expected: The circuit typically uses a Dark Blue wire for the 5V reference, a Brown wire for ground (low reference), and a Dark Blue/White wire for the signal.. Failure: N/A - This is for wire identification during testing.

Scan Tool Commands That Help

• GDS2 / Tech2: Crankshaft Position Variation Learn (Cam/Crank Relearn) — This procedure should be performed after replacing the camshaft sensor, crankshaft sensor, or any major timing components. It helps the ECM synchronize the signals from the new parts and can resolve a persistent P0340 code after a repair has been made.

Wiring & Ground Locations

• G103 (Passenger Side) — On the front of the passenger side (right side) cylinder head.. This is a primary engine ground point. A loose or corroded connection here can cause various sensor and module communication issues, including erratic signals that could trigger a P0340.
• G104 (Driver Side) — On the rear of the driver side (left side) cylinder head.. Another critical engine-to-chassis ground. Poor contact at this location can lead to intermittent electrical faults and sensor codes.
• ECM Connectors (Duramax LML) — Located on the driver's side of the engine, between the power steering reservoir and the battery. The ECM has multiple large connectors, often black and gray.. The camshaft position sensor wiring terminates at one of these connectors. When diagnosing a circuit fault, checking for pin fitment, corrosion, or damage at the ECM connector is a crucial step after checking the sensor end.
• G218 (Interior Ground) — Located under the dash, behind the driver's side kick panel.. While less likely to be the primary cause for a single engine code, this is a known problematic ground on K2XX platform trucks (2014+) that can cause a host of strange electrical issues. If P0340 is accompanied by other seemingly unrelated electrical faults, checking G218 is worthwhile.

Real Owner Repair Stories

• YouTube channel 'GMC Sierra Check Engine Light On Camshaft Sensor Codes P0340 P0341' (2011 GMC Sierra 4.3L V6 (GMT900 platform, similar wiring principles to V8s)) — Check Engine Light with codes P0340 and P0341.
  ❌ Tried (didn't work) The technician immediately suspected a circuit issue rather than a sensor failure.
  ✅ What actually fixed it Using an oscilloscope, the technician found the cam sensor signal was glitching. Wiggling the sensor connector caused the signal to drop out completely. The final diagnosis was a faulty camshaft position sensor connector/pigtail, not the sensor itself.
• YouTube channel '$$$ Troubleshooting Camshaft Circuit Codes in 2008 Silverado with 6.0 Vortec Motor. P0340 & P0341' (2008 Chevrolet Silverado 2500 6.0L V8 (GMT900 platform)) — Intermittent Check Engine Light with codes P0340 and P0341.
  ❌ Tried (didn't work) Initial scan confirmed the codes.
  ✅ What actually fixed it A thorough visual inspection of the wiring harness revealed several wires had rubbed through their insulation against the alternator. The damaged wires, which included the cam sensor circuit, were repaired with heat shrink tubing, and the harness was re-secured. This resolved the codes without replacing the sensor.

Model Year Variations Within This Range

• 2015-2016 (K2XX Platform): TSB #PIP5335D (an update to the cited #PIP5335C) and TSB #PIP5724 point to a specific 16-pin connector, X154, on the front engine cover as a common source of corrosion or pinched wires causing P0340, especially on 2015+ models. This highlights a specific known failure point on the newer generation within this range.