P0385 – Crankshaft Position Sensor “B” Circuit

P0385 is an OBD-II trouble code that points to a problem with the crankshaft position sensor “B” circuit. When this code sets, your engine computer is telling you it’s losing or seeing an incorrect signal from one of the crank sensors it relies on for timing and fuel control. You might notice hard starting, stalling, or a no-start situation, and sometimes the engine runs rough or misfires. In this guide, you’ll learn what P0385 means, common causes, symptoms, how to diagnose it, and what it usually costs to repair.

What Does P0385 Mean?

P0385 stands for “Crankshaft Position Sensor ‘B’ Circuit Malfunction.” On engines with more than one crankshaft position sensor or a multi-channel crank sensor, the “B” designation refers to the second sensor or second signal channel. Your ECU uses this signal to determine crankshaft speed and position so it can control ignition timing and fuel injection.

When the ECU sees a missing, erratic, or out-of-range signal from the “B” circuit, it sets P0385 and usually turns on the check engine light. If the signal is completely gone, the engine may crank but not start, or it may stall unexpectedly.

Quick Reference

• Code: P0385
• Definition: Crankshaft Position Sensor “B” Circuit Malfunction
• Primary concern: Hard start, no-start, or stalling
• Typical causes: Failed crank sensor, wiring fault, damaged tone ring
• Urgency: Medium to high – fix soon to avoid being stranded

Real-World Example / Field Notes

In the shop, I often see P0385 on higher-mileage V6 and V8 engines that use two crank signals or a multi-track reluctor wheel. A common pattern is a customer who reports “cranks a long time before it starts” or “dies at stoplights once in a while.” Scan data will show RPM dropping to zero even though the engine is still spinning. After checking power, ground, and wiring, the crank sensor “B” signal is usually weak or missing on the scope. Replacing the sensor and cleaning corrosion from the connector typically solves the issue.

Symptoms of P0385

• Hard starting – Long crank time before the engine fires, especially when hot or cold.
• No-start condition – Engine cranks but will not start if the crank signal is completely lost.
• Stalling – Random engine stall while driving or at idle, sometimes restarts after cooling.
• Rough running – Hesitation, misfires, or poor acceleration due to incorrect timing data.
• Check engine light – MIL on, often with P0385 as the primary stored code.
• Reduced fuel economy – ECU may run conservative timing strategies, wasting fuel.
• Intermittent performance issues – Problems that come and go with temperature or vibration.

Common Causes of P0385

Most Common Causes

• Failed crankshaft position sensor “B” – Internal sensor failure from heat, age, or contamination.
• Damaged wiring or connector – Broken wires, corrosion, loose pins, or oil-soaked connectors at the sensor.
• Incorrect air gap – Sensor not seated fully or installed with debris between sensor and tone ring.
• Cracked or damaged reluctor/tone ring – Missing teeth or wobble causing an erratic signal.
• Aftermarket sensor quality issues – Cheap sensors with weak output or poor fitment.

Less Common Causes

• ECU/PCM internal fault – Rare, but possible if power, ground, and signal wiring are perfect.
• Engine mechanical damage – Excessive crankshaft end play or a slipped reluctor wheel.
• Previous engine or transmission work – Harness pinched, misrouted, or sensor left loose after repairs.
• Electrical interference – Poor grounds or routing near ignition coils causing noise on the signal wire.
• Low system voltage – Weak battery or charging problems affecting sensor reference voltage.

Diagnosis: Step-by-Step Guide

To diagnose P0385 properly, you’ll want a quality scan tool, a digital multimeter, basic hand tools, and ideally an oscilloscope for viewing the crank signal. Access to wiring diagrams or a factory service manual helps a lot. If you don’t have advanced tools, you can still do basic checks before heading to a shop.

1. Confirm the code and check for companions
   Use an OBD-II scanner to verify P0385 and look for related codes (like other crank/cam sensor codes or misfire codes). Record freeze-frame data to see conditions when the fault occurred.
2. Perform a visual inspection
   Locate the crankshaft position sensor “B” (often near the crank pulley, flywheel, or transmission bellhousing). Inspect the connector for corrosion, broken locks, oil saturation, or damaged insulation on the harness.
3. Check for loose or damaged tone ring
   With the vehicle safely lifted if needed, inspect the reluctor/tone ring teeth where visible. Look for missing, bent, or cracked teeth and check for wobble that could indicate a loose ring.
4. Verify power and ground
   With the key on, use a multimeter to check for proper reference voltage (usually 5 V) and ground at the sensor connector. If either is missing, trace back through the harness and related fuses.
5. Measure sensor resistance
   With the sensor unplugged, measure its resistance and compare it to the specs in a service manual. An open circuit or wildly out-of-range reading usually means the sensor is bad.
6. Check signal output (advanced)
   If you have an oscilloscope, back-probe the signal wire and look for a clean, consistent waveform while cranking or running. Gaps, dropouts, or a flat line confirm a sensor or tone ring issue.
7. Wiggle test the harness
   While watching live RPM data on a scan tool or the scope trace, gently move the harness and connector. If the signal cuts in and out, you’ve found an intermittent wiring problem.
8. Inspect for previous repair damage
   Look for signs of recent work near the sensor area: fresh sealant, new gaskets, or non-factory routing. Harnesses can get pinched between the engine and transmission or left against hot exhaust parts.
9. Clear codes and road test
   After any repair or cleaning, clear the codes and test drive while monitoring live data (RPM, cam/crank sync). If P0385 does not return and the engine behaves normally, the fix is confirmed.

Pro tip: If your scan tool supports Mode $06, check the crankshaft position sensor test results. You can sometimes spot a marginal sensor that hasn’t fully failed yet but is throwing borderline counts or error values.

Possible Fixes & Repair Costs

Most P0385 repairs involve restoring a clean, reliable crank sensor “B” signal to the ECU. Costs vary by vehicle design, labor rates, and how buried the sensor is.

• Replace crankshaft position sensor “B” – The most common fix. Parts typically range from $40–$180, with labor from $80–$250 depending on access. Some sensors are easy to reach; others require removing transmission components.
• Repair or replace wiring/connector – Fixing corroded terminals, broken wires, or a damaged connector can run $50–$200 in labor and small parts.
• Clean or reseat sensor – Removing the sensor, cleaning debris or rust, and reinstalling properly can resolve minor issues at minimal cost if you DIY.
• Replace damaged tone ring/reluctor – This can be more involved, sometimes requiring transmission or crankshaft-related work. Expect $300–$900+ depending on the vehicle.
• ECU replacement or reprogramming – Rare, but if needed, can cost $500–$1,200 including programming.

In general, you’re looking at a typical repair range of about $150–$500 for most P0385 fixes, with higher costs if the sensor is hard to access or the reluctor ring is damaged. Labor rates, OEM vs. aftermarket parts, and shop diagnostic time all affect the final bill.

Can I Still Drive With P0385?

Often, you can still drive with P0385 for a short time, but it’s risky. If the sensor signal is only partially failing, the engine may run with occasional hiccups, long cranking, or random stalls. The problem is that a marginal crank sensor can go from intermittent to dead without warning, leaving you with a no-start in a parking lot or on the side of the road. If the vehicle is running, drive it only as needed and schedule diagnosis and repair as soon as possible.

What Happens If You Ignore P0385?

Ignoring P0385 can lead to frequent stalling, hard starts, and eventually a complete no-start condition. In some cases, the ECU may run overly conservative timing, hurting fuel economy and performance. Repeated stalling in traffic is also a safety risk. Catching and fixing the issue early usually keeps the repair simple and avoids being stranded.

Related Sensor Crankshaft Codes

Compare nearby sensor crankshaft trouble codes with similar definitions, fault patterns, and diagnostic paths.

• P0335 – Crankshaft Position Sensor “A” Circuit
• P0390 – Camshaft Position Sensor “B” Circuit Bank 2
• P0365 – Camshaft Position Sensor “B” Circuit Bank 1
• P0339 – Crankshaft Position Sensor “A” Circuit Intermittent
• P0338 – Crankshaft Position Sensor “A” Circuit High
• P0337 – Crankshaft Position Sensor “A” Circuit Low

Key Takeaways

• P0385 points to a malfunction in the crankshaft position sensor “B” circuit, often due to a failing sensor or wiring issue.
• Symptoms include hard starting, stalling, rough running, and a check engine light.
• Basic checks you can do at home include visual inspection of the sensor and connector, and code clearing after simple repairs.
• Most repairs involve replacing the sensor or repairing wiring, typically costing between $150 and $500.
• Driving with P0385 is possible but risky; a complete no-start can happen without warning, so don’t delay diagnosis.

Vehicles Commonly Affected by P0385

P0385 shows up across many brands, but it’s especially common on engines that use multiple crank signals or complex reluctor wheels. You’ll often see this code on:

• GM/Chevrolet/GMC – V6 and V8 trucks and SUVs, such as Silverado, Sierra, Tahoe, and TrailBlazer.
• Ford/Lincoln – Modular V8 engines and some V6 applications, especially in trucks and larger sedans.
• Nissan/Infiniti – V6 engines like the VQ series in Altima, Maxima, Pathfinder, and related models.
• Toyota/Lexus – Certain V6 and V8 engines where crank sensors sit near the transmission bellhousing.
• Chrysler/Dodge/Jeep – V6 and V8 engines in SUVs and trucks, particularly older models with higher mileage.

Any OBD-II vehicle with a dual-crank or multi-channel crank sensor design can set P0385, so always check your specific service information.

FAQ

Can I clear P0385 and keep driving if the car seems fine?

You can clear the code, but if the underlying problem isn’t fixed, P0385 will usually return. The car may seem fine now, but an intermittent crank sensor can fail suddenly and cause a no-start. Use code clearing only after repairs or as a temporary step to confirm a fix.

Is P0385 the same as a bad camshaft sensor?

No. P0385 refers specifically to the crankshaft position sensor “B” circuit. While crank and cam sensors work together, they are separate components. A bad cam sensor has its own set of codes (like P0340). However, both can cause similar symptoms, so proper diagnosis is important.

How do I know if it’s the sensor or the wiring causing P0385?

The best way is to test. Check for proper power and ground at the sensor connector, inspect the harness for damage, and measure sensor resistance. If power and ground are good and the sensor is out of spec or has a weak signal on a scope, the sensor is likely bad. If voltage is missing or changes when you move the harness, you probably have a wiring issue.

Can a weak battery cause P0385?

A weak battery usually doesn’t directly cause P0385, but low system voltage can aggravate marginal sensors and make intermittent issues show up more often. If you have slow cranking or low voltage codes along with P0385, test and correct battery and charging system problems as part of the diagnosis.

How urgent is it to fix P0385?

It’s not something to ignore. While you might be able to drive for a bit, a failing crank sensor can leave you stranded with a no-start at any time. Stalling in traffic is also a safety concern. Plan to diagnose and repair P0385 as soon as your schedule allows, rather than waiting for it to get worse.