P0371 — Timing Reference High Resolution Signal “A” Too Many Pulses #

Note: The code label may vary depending on the vehicle manufacturer.

Known label variations by OEM:

• “Timing Reference High Resolution Signal A Excess Pulses” (GM)
• “Crankshaft Position Sensor Signal A Too Many Pulses” (Ford)
• “Engine Position Sensor A Excessive Pulses Detected” (Chrysler)
• “High-Resolution Timing Reference A: Too Many Signals” (Toyota)

Code summary for P0371 #

P0371 is a generic powertrain diagnostic trouble code (DTC) triggered when the engine control module (ECM) detects an excessive number of timing reference pulses from the high-resolution sensor “A” circuit during a given engine cycle. The high-resolution timing reference typically comes from a sensor—often the crankshaft position sensor (CKP) or camshaft position sensor (CMP)—which provides precise information about engine speed and position. When the ECM receives more pulses than expected, it interprets this as a malfunction, which could affect fuel injection and ignition timing. This code is relevant for most OBD-II/EOBD-compliant vehicles. While it may not always cause immediate drivability issues, addressing it promptly is vital for long-term engine performance and reliability.

Frequent symptoms for code P0371 #

Drivers and technicians may notice a range of symptoms when P0371 is set. Sometimes, the issue is subtle and only revealed through the check engine light, but it can also manifest as noticeable performance concerns. Common symptoms include:

• Check Engine Light (CEL) illuminated
• Hard starting or extended cranking
• Rough idle or engine misfire
• Reduced engine performance or hesitation
• Intermittent stalling, especially at low speeds
• Poor fuel economy
• In some cases, no observable symptoms besides the DTC

Probable causes for code P0371 (ranked by frequency) #

The root causes for P0371 generally relate to sensor faults, wiring issues, or problems with the timing system. Some are more common than others. Below are the most likely culprits, in order of how frequently they occur:

1. Faulty or failing crankshaft position sensor (CKP)
2. Damaged or corroded sensor wiring/connectors
3. Faulty camshaft position sensor (CMP)
4. Misaligned or damaged sensor reluctor ring (the toothed wheel or trigger for the sensor)
5. Electrical interference (EMI) from aftermarket electronics or poor grounds
6. ECM/PCM software glitches or internal failure (rare)
7. Improperly installed aftermarket performance parts (e.g., underdrive pulleys)

Step-by-step diagnosis for code P0371 #

A systematic approach is crucial for diagnosing P0371 efficiently and avoiding unnecessary parts replacement. Here’s a proven step-by-step process:

• 1. Verify the code: Use an OBD-II scanner to confirm P0371 is present and check for related codes (especially those relating to CKP or CMP sensors).
• 2. Inspect wiring and connectors: Visually check the sensor wiring harness for damage, corrosion, or loose connectors. Pay special attention to areas near moving engine parts.
• 3. Check the high-resolution sensor “A”: Using a multimeter or oscilloscope, test the crankshaft and camshaft position sensors for correct resistance and signal output.
• 4. Inspect the reluctor ring: Ensure the reluctor (trigger) wheel or ring attached to the crankshaft/camshaft is intact, clean, and properly aligned. Damaged or missing teeth can cause erratic signals.
• 5. Test for electrical interference: Look for aftermarket electronics, poor grounds, or routed wires that may induce noise into the sensor circuit.
• 6. Clear the code and road test: After repairs or adjustments, clear the code and perform a test drive to ensure the DTC does not return.
• 7. ECM/PCM evaluation: If all mechanical and electrical checks pass, consider possible ECM/PCM malfunction—consult OEM service information for advanced testing.

Possible repairs for code P0371 #

Repairs for P0371 should target the root cause identified during diagnosis. It’s important not to simply replace parts without proper testing. Common fixes include:

• Replace faulty crankshaft or camshaft position sensor
• Repair or replace damaged wiring/connectors
• Clean, repair, or replace a damaged reluctor (trigger) ring
• Reroute or shield wiring to eliminate electrical interference
• Update or reflash ECM/PCM software if a known glitch exists (OEM service bulletin)
• Replace ECM/PCM only if all other causes have been ruled out

Is it safe to drive with code P0371? #

Driving with P0371 is generally not recommended. While some vehicles may continue to operate with minimal symptoms, the risk of poor engine performance, sudden stalling, or even the engine failing to start increases. At best, you may experience reduced fuel economy and drivability. At worst, you may be left stranded or cause further damage by ignoring the underlying issue. For your safety and to prevent costly repairs, it’s wise to address this DTC as soon as possible.

Vehicles most commonly affected by P0371 #

P0371 is a generic OBD-II code, but some makes and models tend to experience it more frequently, especially those with known sensor or wiring vulnerabilities. These include:

• Chevrolet Silverado, Tahoe, Suburban (especially 1999–2007)
• Ford F-150, Expedition (2004–2014)
• Dodge Ram 1500/2500 (2002–2010)
• Toyota Tacoma, Tundra (2005–2015)
• Jeep Grand Cherokee, Wrangler (2005–2012)
• Some Volkswagen and Audi models (with V6/V8 engines)

Common mistakes & best practices for P0371 #

Misdiagnosis and unnecessary parts replacement are frequent pitfalls with P0371. To ensure efficient and accurate repair, keep these points in mind:

• Don’t replace the sensor without first inspecting wiring and connectors—corrosion or loose pins are often the true culprits.
• Avoid skipping the reluctor ring check; missing or damaged teeth can easily be overlooked.
• Don’t ignore the possibility of electrical interference from non-OEM electronics or poor grounds.
• Always clear the code and retest after each repair step to confirm the issue is resolved.
• Consult OEM service bulletins for your specific vehicle—sometimes a simple software update is the fix.

Express FAQ: P0371 #

Still have questions? Here are quick answers to the most common concerns:

• Q: Will P0371 cause my car to not start?
  A: It can, especially if the timing signal is disrupted enough to confuse the ECM. However, in many cases the engine will start but may run poorly.
• Q: Can a bad battery or alternator trigger P0371?
  A: Unlikely. While low voltage can cause a range of issues, P0371 typically points to a signal problem in the timing reference circuit, not a general power supply fault.