If your scan tool shows a P0335 error “Crankshaft Position Sensor ‘A’ Circuit Malfunction” and you’ve already ruled out a faulty sensor or broken timing component, the wiring harness is the next logical place to look. A break, short, or high-resistance connection in the harness can stop the crankshaft position (CKP) signal from reaching the PCM, triggering this code even with a good sensor installed. Checking wiring harness continuity for P0335 error isn’t guesswork it’s a targeted, step-by-step verification that confirms whether the physical path between the sensor and the engine control module is intact.

What does “checking wiring harness continuity for P0335 error” actually mean?

It means using a multimeter to test whether electricity can flow freely along each wire in the CKP sensor circuit specifically the signal wire, power feed (if applicable), and ground path. Continuity testing checks for open circuits (a complete break), while resistance testing helps spot partial failures like corrosion or damaged insulation that may not fully open but still disrupt the signal. This isn’t about testing every wire in the car just the three critical ones tied to the crankshaft position sensor: the signal line going to the PCM, its dedicated ground, and its 5V or 12V reference supply (depending on sensor type).

When should you do this and why not skip it?

You should check wiring harness continuity for P0335 error when:

  • The CKP sensor tests fine off the vehicle (e.g., resistance within spec, clean pins),
  • You’ve confirmed the sensor has proper power and ground at its connector with the key on,
  • The P0335 returns after replacing the sensor with a known-good unit,
  • You see visible damage near the sensor connector, firewall pass-through, or under the intake manifold common trouble spots on many GM, Ford, and Chrysler engines.

Skipping this step often leads to misdiagnosis swapping sensors repeatedly or overlooking a chafed wire behind the starter that only fails when the engine vibrates.

How to test continuity without missing the real issue

Start with the ignition off and battery disconnected. Unplug both ends: the CKP sensor connector and the corresponding PCM connector (use a factory wiring diagram to identify the correct pins don’t guess). Set your multimeter to continuity or lowest ohms scale. Touch one probe to the CKP signal pin at the sensor end, the other to the matching signal pin at the PCM end. You should read near-zero ohms (or hear a beep). Repeat for the ground and reference voltage wires.

A reading of “OL” (open loop) means a break somewhere in that wire often near sharp brackets, heat sources, or where harnesses flex near moving parts. A reading over 1–2 ohms suggests corrosion, crimp damage, or a poor splice especially if it changes when you gently wiggle the harness.

Common mistakes people make during this test

Testing continuity with the connectors still plugged in that gives false readings because internal PCM or sensor circuitry creates alternate paths. Assuming “no continuity = bad wire” without checking for intermittent faults a wire might show continuity cold but open when warmed or flexed. Using the wrong pins due to outdated or non-OEM diagrams some vehicles share grounds across multiple sensors, so verifying the exact CKP ground path matters. Also, forgetting to test the ground circuit back to the PCM, not just to the engine block a bad ground at the PCM connector will mimic a sensor failure.

That’s why it’s important to verify the ground path all the way to the PCM, not just confirm it’s bolted to the engine.

What to do if continuity looks good but the code stays

Good continuity doesn’t guarantee a healthy signal circuit. High resistance in the ground or reference wire even below 5 ohms can distort the signal enough to set P0335. That’s where measuring actual resistance under load adds value. Also inspect the CKP connector itself: bent pins, moisture, or green corrosion on terminals are frequent culprits that won’t show up on a basic continuity test. For example, a slightly oxidized ground pin may pass continuity but fail to carry the small current needed for a clean square-wave signal.

If you find discoloration or flaking on the pins, cleaning or replacing the connector often resolves the issue faster than chasing harness damage.

Practical next step

Grab your multimeter, a factory wiring diagram (or trusted source like ALLDATA), and a small flashlight. Start at the CKP sensor: unplug it, identify the three wires (signal, ground, reference), then trace them visually as far as you can toward the PCM. Look for pinch points, melted insulation, or rodent damage before you even turn the meter on. Then test each wire end-to-end and retest while gently bending or tapping sections of the harness near known stress points. If continuity fails on one wire, isolate the break by testing shorter segments until you find the fault.