P0335 Code on a Buick: Crankshaft Position Sensor A Circuit (Buick Guide)

P0335 is GM's "Crankshaft Position (CKP) Sensor A Circuit." It means the engine computer stopped seeing crankshaft pulses when it should have — while the starter was turning the engine, or while the engine was running. Because a Buick cannot time spark or fuel without that signal, P0335 usually comes with a no-start, a stall or a stumble. The reflex is to buy a crank sensor, and sometimes that is right. But GM's documents for Buick models describe other causes: a weak battery on low-mileage 2017–2018 Encores, a harness rubbing on the back of the cylinder head on 2010–2011 Enclaves, and, on the Encore GX 1.2L, a reluctor that cuts into the rear main seal housing because crankcase pressure got too high. In that last case a new sensor will fail again.

What Does P0335 Mean on a Buick?

The crankshaft position sensor reads a toothed reluctor wheel on the crankshaft. From it, the engine computer knows engine speed and exactly where each piston is, which it needs to fire the spark plugs and injectors at the right moment. The camshaft sensors then tell it which stroke each cylinder is on.

GM separates crank sensor faults into two codes:

• P0335 — Circuit. Crank pulses are missing.
• P0336 — Performance. Pulses are there but the count or pattern is wrong.

Stop/start Buicks such as the 2018 Enclave add another crank code, P034B (crankshaft direction incorrect). Of the group, P0335 is the "no signal" code — which is why it so often goes with a no-start.

How GM's P0335 Test Works

GM's 2015 OBD summaries spell out the P0335 logic for the 3.6L (Enclave, LaCrosse), the 1.4T (Encore) and the 2.0T/2.4L (Regal, Verano). The ECM sets P0335 when:

• the starter is engaged, the camshaft sensors are sending pulses (or the mass airflow sensor shows air moving), and no crank pulse arrives for 4 seconds; or
• the engine is running and crank pulses stop for as little as 0.1 second (1.0 second in GM's 2.0T/2.4L group).

It runs continuously and is a two-trip code. Two details are worth noticing. First, the ECM uses the cam sensors as the witness — if the cams are turning and the crank signal is not, the crank circuit is blamed. Second, the running test is extremely short: a connection that drops out for a tenth of a second is enough. That is why chafed wiring and loose terminals are as common as failed sensors.

For comparison, GM's P0336 test counts crank teeth: on the 3.6L it fails if one revolution produces fewer than 51 or more than 65 pulses, or if the ECM has to resynchronize ten times in under ten seconds. Damaged reluctor teeth and electrical noise usually show up there.

Encore 1.4T: Test the Battery First

GM's preliminary information PIP5482B covers the 2017–2018 Encore with the 1.4L LUV (and the Trax and Malibu) with P0335, P0340 and P0365 set together, current or in history. GM says it occurs only on vehicles with very low miles or that sat for an extended time, and that it may have been caused by a low battery state of charge during two consecutive starts.

GM's procedure:

1. Test the battery with GM's GR8 / EL-50313-20 tester.
2. If it passes, clear the codes and start the engine twice.
3. If the codes do not return, do not attempt further repairs — return the vehicle.
4. If they return, perform normal diagnostics.

That is a crank sensor code, a cam sensor code and an exhaust cam sensor code all at once, with the fix being a charged battery. GM also published an engineering information document (PIE0416A) on 2017 Encores with P0335, P0340 or P0365, which closed its field information request and directs technicians to service information. If an Encore that has been sitting shows that trio, test the battery before buying three sensors.

Encore GX 1.2L: Crank Sensor and Reluctor Damage

For the 2020–2021 Encore GX with the 1.2L LIH three-cylinder, GM's PIP5761 describes a crank-no-start or check engine light with P0335 or P0336, sometimes with an oil leak at the rear of the engine. GM's cause is a damaged crank sensor and reluctor.

The mechanism is unusual: GM says crankcase pressure can rise abnormally because of an internal restriction in the cam cover's PCV channel, making the rear main seal housing cover balloon outward until it touches the reluctor. GM's steps:

• Remove and inspect the crank sensor. If it is undamaged, continue with normal diagnosis.
• If it is damaged, remove the reluctor and inspect the rear main seal housing.
• If the reluctor has cut through the housing, GM calls for engine replacement because of metal contamination in the oil.
• If not, replace the crank sensor, reluctor, rear main seal housing and the cam cover.

The cam cover is the root cause. Replacing only the crank sensor leaves the PCV restriction in place. The 1.3L L3T Encore GX is not listed in this document; check your engine code.

Enclave and LaCrosse 3.6L

Harness chafing (2010–2011 Enclave). A GM preliminary information index entry, PI-0220, lists a check engine light with P0300, P0303, P0306, P062B, P0698, P0532, P0335, P0222 or P0122 on 2010–2011 Enclave, Traverse and Acadia models. The cause given is the engine wiring harness contacting the back of the bank 2 cylinder head. We have read only GM's index summary, not the document itself. A list of unrelated codes like that — misfires, sensor reference faults, a crank code — is the signature of a harness problem, not of several bad parts.

Crank sensor circuit interference (2018 Enclave). GM's 17-NA-317 covers the 2018 Enclave LFY with P034B (crank direction incorrect), P0506, cam phaser codes and P0557, plus transmission shudder, stalls after auto start and Reduced Engine Power messages. The cause is the crank sensor circuit picking up interference from another circuit in the same harness; the fix is a twisted-pair jumper harness from the sensor to the ECM and a G109 ground inspection. It does not name P0335, but it shows how sensitive the crank signal is to wiring on these engines.

2017 LaCrosse 3.6L. GM's 17-NA-156 covers P0336 on the 2017 LaCrosse LGX with the 8-speed: noise on the crank sensor line creates too many pulses, and the fix is an ECM reprogram — no parts. The earlier PI, PIP5464, told technicians not to replace any parts.

Correlation codes on the 3.6L (P0016–P0019) are a different subject: GM's PIP3423 traces some to a crank reluctor that has slipped on the crankshaft. That reluctor problem moves the timing reference rather than killing the signal, so it does not normally set P0335.

Regal and Verano 2.0T: Debris on the Reluctor

GM's PIP5613 covers the 2011–2013 Regal and 2013–2016 Verano with the 2.0L turbo LHU and P0336, often with an inoperative or erratic tachometer and extended crank or no-start. GM's cause is a damaged crankshaft reluctor, and notes that it "only takes a small amount of damage" — a ding or small dent — to cause the problem. GM's tip for a no-start: unplug the crank sensor and see whether the engine starts normally. The damage can come from foreign material in the oil pan, such as pieces of a broken timing chain guide, so GM says to find and fix the source. If those teeth are damaged badly enough to lose the signal, P0335 is the next step.

Symptoms of P0335 on a Buick

• Crank-no-start, or a long crank before starting
• Stalling, especially hot or over bumps (wiring)
• Tachometer dropping to zero or acting erratically while driving
• Check engine light, often with P0336, P0340 or P0365
• Misfire codes alongside it (harness damage)
• Oil leak at the rear of the engine (Encore GX 1.2L)

Causes and How to Confirm Each

How Is P0335 Diagnosed on a Buick?

1. Write down every code and whether each is current or history. P0335 with P0340 and P0365 is a different case from P0335 alone.
2. Test the battery and charging system. On an Encore that has been sitting, GM's first step is the battery test.
3. Check the engine code. The Encore GX 1.2L, 1.4T Encore, 3.6L and 2.0T each have their own GM document.
4. Watch engine RPM on a scan tool while cranking. Zero RPM with the engine turning confirms no crank signal.
5. Inspect the harness and connector along their whole route — on a 2010–2011 Enclave, at the back of the bank 2 head.
6. Scope the crank sensor signal if possible and check its power, ground and signal circuits per service information.
7. Remove and inspect the sensor. Damage to the tip means something is touching the reluctor — find out what before fitting a new one.
8. After replacing the sensor or ECM, check service information for whether a crankshaft position variation relearn is required on your engine.

Parts and Cost

GM Documents That Name P0335 on Buick Models

Have a dealer check your VIN against current bulletins and coverages rather than relying on any article, including this one.

What Other P0335 Pages Get Wrong

• "P0335 means replace the crank sensor." GM's Encore document says test the battery and, if the codes do not return, do nothing else.
• Replacing a damaged sensor without asking why. On the Encore GX 1.2L, the cause is the reluctor rubbing a ballooned seal housing; the cam cover is part of GM's fix.
• Ignoring wiring. GM's running test fails on a 0.1-second dropout, and GM has Buick documents for harness chafing and circuit interference.
• Mixing up P0335 and P0336. Missing signal is P0335; a wrong tooth count is P0336.
• Treating three sensor codes as three bad sensors. P0335 with P0340 and P0365 together points at something they share — battery voltage, a connector, a ground.

For the code on other GM brands, see our P0335 GM guide.

Frequently Asked Questions

Will a Buick start with P0335?

Often not. GM's test sets P0335 when the starter is turning the engine and no crank pulses arrive. If the signal drops out intermittently, the engine may start sometimes and stall at other times.

Why does my low-mileage Encore show P0335, P0340 and P0365?

GM's PIP5482B covers exactly that on 2017–2018 Encores that sat or have very low miles: a low battery during two consecutive starts. Test the battery, clear the codes and start twice.

Can a weak battery cause P0335?

Yes, on some Buicks. GM documented it on the Encore. A battery and charging test costs little and should come before any sensor.

My Encore GX won't start and has P0335 — is it just the sensor?

Possibly, but on the 1.2L, GM's PIP5761 says inspect the removed sensor. If it is damaged, the reluctor and rear main seal housing need checking, and the cam cover is replaced to fix the crankcase pressure cause.

Is P0335 dangerous while driving?

It can be, because the engine may stall without warning. Have it diagnosed before relying on the vehicle for highway driving.

Do I need a relearn after replacing a Buick crank sensor?

Many GM engines need a crankshaft position variation relearn after a crank sensor, reluctor or ECM replacement. Check the procedure for your engine in service information.