📋 Quick Facts
Time
15 minutes
Difficulty
Moderate
Tools
3 tools
Cost to DIY
$25-50
The CKP sensor tells the ECU where each piston is - critical for spark timing and fuel injection. There are two main types: inductive (2-wire, makes its own AC signal from a magnet) and Hall-effect (3-wire, needs a 5V supply, outputs a square wave). The test differs by type.
🛠 What You'll Need
- Digital multimeter (AC + DC volts + ohms) (shop a digital multimeter on Amazon)
- OBD2 scanner with live RPM data (shop a Bluetooth OBD2 scanner on Amazon)
- Back-probe pin set (shop back-probe pin set on Amazon)
- Service manual or wiring diagram
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⚠ When NOT to DIY thisCKP testing often requires cranking the engine with the sensor exposed. Keep hands and clothing away from the timing belt/chain area. Never crank without the keys in your control and the parking brake set.
🎯 Expected Readings (Pass/Fail Reference)
| Inductive (2-wire) sensor resistance | 200 - 1,500 ohms (check service manual) |
| Inductive AC output during cranking | 0.2 - 2.0 V AC, rising with engine speed |
| Hall (3-wire) supply voltage | 5 V or 12 V (depending on car) |
| Hall sensor signal during cranking (DC volts) | Pulses between 0 V and 5 V (or 0 to 12) |
| Sensor air gap (when installed) | 0.020" - 0.050" typical. Bigger gap = weak signal |
| Live RPM during crank (scan tool) | 150 - 300 RPM. Stuck at 0 RPM = CKP not signaling |
Numbers are typical. Always cross-check against your factory service manual for the exact spec.
📝 Step-by-Step Test Procedure
- Confirm with codes and symptomsP0335 (circuit), P0336 (range/performance), P0337 (low), P0338 (high), P0339 (intermittent). Symptoms: cranks but will not start, stalls at speed, hard cold start when sensor heats up.
- Watch live RPM during crankPlug in scanner, watch engine RPM live data. Crank the engine. RPM should jump to 150-300. If it stays at 0 while cranking, the CKP is not producing a signal.
- Identify sensor type and locate it2-wire = inductive (passive). 3-wire = Hall-effect (active). Located on the timing cover, bell-housing, or near the crank pulley. Service manual will show exact location.
- Inductive sensor resistance testUnplug the sensor. Probe between the two pins. Should read 200-1,500 ohms (varies by car). Infinity = open coil. Near 0 = shorted.
- Inductive sensor AC output during crankReconnect, back-probe both wires. Multimeter on AC volts (2V range). Crank for 5 seconds. Should see 0.2-2 V AC. No reading = sensor not producing signal, or reluctor wheel damaged.
- Hall sensor supply checkUnplug, key on. Multimeter on DC volts. Probe between the supply pin (usually red) and ground pin (usually black). Should read 5V or 12V steady. No supply = wiring/ECU problem, not the sensor.
- Hall sensor signal check (back-probe during crank)Reconnect. Back-probe the signal wire while cranking. Multimeter on DC volts. Should pulse between 0 V and 5 V (or 12 V) rapidly. A flat reading = bad sensor.
- Check the reluctor wheel and air gapRemove the sensor and inspect the teeth on the reluctor (the toothed wheel the sensor reads). Missing teeth, debris, or excessive gap will cause erratic signals. Reinstall with the correct air gap (often a non-magnetic feeler gauge or paper spacer for snap-fit sensors). shop crankshaft position sensors on Amazon.
✅ Pass / Fail Criteria
✅ PASS
Resistance in spec, clean AC or pulsed DC output during crank, RPM signal shown on scanner, no missing reluctor teeth, correct air gap
❌ FAIL
No resistance reading, no output during crank, 0 RPM on scanner while cranking, damaged reluctor wheel, or wrong supply voltage
🔧 If It Fails - What To Do Next
Replace the sensor (OEM-quality is worth the extra few dollars - cheap aftermarket CKPs have a high failure rate). Some cars require relearn procedure with a scan tool after install. See What is a crankshaft position sensor? and Why won't my car start?
🔗 Related Guides
❓ Frequently Asked Questions
What does a bad CKP sensor feel like?
No-start (cranks but never fires), random stalls (especially when hot), or hard restart after the car sits for 5 minutes.
Can I drive with a bad crankshaft sensor?
Maybe briefly - many cars will not start at all without it. Replace immediately if any of the symptoms appear.
What is the difference between CKP and CMP sensors?
CKP reads crankshaft position; CMP reads camshaft. ECU compares the two to identify which cylinder is on its compression stroke for fuel/spark timing.
Why does my CKP fail when hot?
The internal electronics expand with heat and break a marginal solder joint. Classic "starts cold, stalls hot" pattern.
Do I need to relearn after replacing a CKP?
On many GM and Chrysler vehicles, yes - a scan tool relearn lets the ECU map the reluctor teeth. Check the service manual.
How long does a CKP sensor last?
100,000+ miles. Heat is the main killer.