Crankshaft and camshaft position sensor comparison

The purpose of this test is to directly compare the relative positions of the Crankshaft position (CKP) and Camshaft position (CMP) sensor waveforms and features.

How to perform the test

View connection guidance notes.

1. Use manufacturer’s data to identify the crankshaft and camshaft sensor signal circuits.
2. Connect PicoScope Channel A to the crankshaft circuit.
3. Connect PicoScope Channel B to the camshaft circuit.
4. Minimize the help page. You will see that PicoScope has displayed an example waveform and is preset to capture your waveform.
5. Start the scope to see live data.
6. Start the engine and run at idle.
7. With your waveforms on screen stop the scope.
8. Turn off the engine.
9. Use the Waveform Buffer, Zoom and Measurements tools to examine your waveform.

Example waveform

Waveform notes

These known good waveforms have the following characteristics:

• A digital CKP sensor signal (Channel A) switching from just above 0 V to just below 5 V.
• A periodic decrease in the CKP switching frequency, causing it to appear almost halved.
• A digital CMP sensor signal (Channel B) switching from just above 0 V to just below 5 V.
• Each cylinder specific phase of the camshaft rotation indicated by the relative switching periods of the CMP sensor signal.
• One complete CMP sensor waveform cycle for every two complete CKP waveform cycles.
• Stable voltage levels, whether around 0 V or around 5 V, on both channels.
• Clean transitions between the digital signal voltage levels, on both channels.
• No excessive hash or intermittent signal drop outs, on either channel.
• Overall switching frequencies that increase with increasing engine speed, on both channels.
• No variation in the waveform pattern positions with respect to each other (they should not shift with time), given fixed engine operating conditions.

Waveform Library

Go to the drop-down menu bar at the lower left corner of the Waveform Library window and select Crankshaft sensor (Hall effect) or Camshaft sensor (Hall effect).

Further guidance

An engine’s CKP and CMP sensors provide the Engine Control Module (ECM) with critical engine speed, position, and timing reference data.

For the engine to function properly, the engine must be timed correctly and the sensors and related apparatus must be fixed in the correct position relative to the crankshaft and camshaft(s).

The measurements in this test allow you to directly compare CKP and CMP sensor waveforms, for example, to check that their positions are fixed, and not moving, relative to each other. The measurements can also be compared to manufacturer data or to known good CKP/CMP sensor waveforms (such as those found within the PicoScope Waveform Library).

PicoScope’s Rulers and Measurements tools enable you to identify in degrees (or the number of teeth) between the relative positions of CKP and CMP reference marks.

You may need to check the individual CKP and CMP sensors are functioning correctly before performing the comparisons in this test. Equally, your system may be fitted with other variations of these timing sensors. In which case, we provide Guided tests to show you how to obtain waveforms from them:

• CKP sensor inductive (floating) voltage, during running
• CKP sensor inductive (referenced) voltage, during running
• CKP sensor Hall voltage, during running
• CMP sensor inductive voltage
• CMP sensor Hall voltage
• CMP sensor AC excited voltage

Any misalignment of the crankshaft and camshaft sensors, or related components, can cause symptoms, such as:

• Engine cranking but not starting
• Engine cutting out
• Erratic running
• Misfires
• Limp-home mode operation
• Malfunction Indicator Lamp (MIL) illumination
• Diagnostic Trouble Codes (DTCs)

Related failures are:

• Discrepancies in crank and valvetrain timing caused by:
  • Incorrectly fitted, worn, damaged, or stretched timing belt/chain
  • Incorrectly fitted, worn, or damaged pulleys, idlers and tensioners
  • Incorrectly fitted, worn, or damaged variable valve timing mechanisms
• Timing reference component faults, such as:
  • Incorrectly fitted or damaged phase wheel
  • Incorrectly fitted or damaged flywheel

Diagnostic trouble codes

Selection of component related Diagnostic Trouble Codes (DTCs):

P0335

P0336

P0337

P0338

P0339

P0340

P0341

P0342

P0343

P0344

P0345

P0346

P0347

P0348

P0349

P0365

P0366

P0367

P0368

P0369

P0390

P0391

P0392

P0393

P0394

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GT151