Hi have 2001 chevy s1o pick up have engine light on with code po335 crank sensor circuit problem had sensor and pig tail connector replaced still have same problem around 2500 rpm engine brakes up engine light pop up. please help

P0335 - Crankshaft Position Sensor A Circuit Malfunction

The crankshaft position sensor (CKP) measures crankshaft location and relays this information to the PCM (Powertrain Control Module). Depending on the vehicle, the PCM uses this crankshaft position information to time the spark properly or on some systems it is only for misfire detection and does not control spark timing. The CKP sensor is stationary and works in harmony with a reluctor ring (or toothed ring) that is attached to the crankshaft. As this reluctor ring passes in front of the CKP sensor, the magnetic field created by the CKP sensor is interrupted and this creates a square wave voltage signal that the PCM interprets as crankshaft position. If the PCM detects that there are no crankshaft pulses or if it sees a problem with the pulses on the output circuit, P0335 will set.

Symptoms:
NOTE: If the crank sensor is used only for misfire detection and NOT spark timing (this varies with the vehicle), the vehicle should start and run with MIL (Malfunction indicator lamp) illumination. Also, some vehicles require several key cycles to illuminate the MIL. If this is the case, there may be no MIL illumination until the problem often enough over time. If the crank sensor is used for BOTH misfire detection and spark timing, the vehicle may or may not start. Symptoms may include:
* Vehicle may not start (see above)
* Vehicle may run rough or misfire
* MIL illumination

Causes: A P0335 "check engine light" code could be caused by:
* Damaged CKP sensor connector
* Damaged reluctor ring (missing teeth or not turning due to sheared-off keyway)
* Sensor output open
* Sensor output shorted to ground
* Sensor output shorted to voltage
* Failed crank sensor
* Broken timing belt
* Failed PCM

Possible Solutions:
1. Using a scan tool, check if, when engine is running or cranking, that there is an RPM signal.
2. If there is no RPM reading, then visually inspect the crank sensor and connector for any damage and repair as necessary. If there is no visible damage, and you have access to a scope, you could check the CKP 5 Volt square wave pattern. If you do not, then, obtain a resistance reading of your crank sensor from a repair manual. (There are so many different types of crank sensors that there's no way to put here which resistance reading is correct). Then check the resistance of the CKP sensor by disconnecting the sensor and measuring resistance of the sensor. (It is best to check resistance readings from the PCM connector. This rules out any wiring problems from the start. But it does require some mechanical skill and shouldn't be performed if you\'re not familiar with automobile electrical systems). Is the sensor within resistance specs?
3. If not, replace the CKP sensor. If so, recheck resistance reading from the PCM connector. Is the reading still okay?
4. If not, repair open or short in the wiring to the crank sensor and re-check. If the reading is okay, the problem is intermittent or the PCM may be at fault. Try reconnecting and checking for RPM signal again. If there is now an RPM signal, wiggle test the wiring harness to try and induce the fault.

This code is basically identical to P0385. This code P0335 refers to Crankshaft Posistion Sensor "A", whereas P0385 refers to Crankshaft Position Sensor "B". Other crank sensor codes include P0016, P0017, P0018, P0019, P0335, P0336, P0337, P0338, P0339, P0385, P0386, P0387, P0388, and P0389.

Test it and keep us updated.