Safety Warning
DIY auto repair can cause serious injury, fire, or vehicle damage. These guides are for informational purposes only. Always follow OEM torque specs, wear PPE, and consult a certified mechanic if you are unsure. You are solely responsible for your safety.
DTC P0337/16721 - Crankshaft Position Sensor CKT Low Input
1996 Audi A4 Base, StandardSECTION DTC P0337/16721 - Crankshaft Position Sensor CKT Low Input
NOTE:
DTC is set when crankshaft position sensor signal is not seen for more than 3 seconds with engine speed 25-400 RPM.
- Inspect Crankshaft Position (CKP) sensor connector for looseness and/or corrosion. CKP sensor is located on driver side of cylinder block. Repair sensor connector as necessary. If sensor connector was not repaired, go to next step. If sensor connector was repaired, erase DTC memory and test drive vehicle.
- Ensure CKP sensor is correctly installed. Check distance between CKP sensor and groove on crankshaft. Maximum distance is .053" (1.3 mm). Repair as necessary. If sensor installation was not repaired, go to next step. If sensor installation was repaired, erase DTC memory and test drive vehicle.
- Disconnect CKP sensor connector. Using a DVOM, measure resistance between CKP sensor connector (sensor side) terminals No. 1 and 2. Resistance should be approximately 1000 ohms. If resistance is to specification, go to next step. If resistance is not to specification, replace CKP sensor. Erase DTC memory and test drive vehicle.
- Connect DVOM between CKP sensor connector (sensor side) terminals No. 1 and 3, then terminals No. 2 and 3. Resistance should be infinite (open). If resistance readings are infinite, go to next step. If resistance readings are not infinite, replace CKP sensor. Erase DTC memory and test drive vehicle.
- Turn ignition off. Disconnect Powertrain Control Module (PCM) connectors. Connect VAG 1598/19 test box to PCM wiring harness. Terminal assignments of test box are identical to PCM connectors "A", "B", "C", "D" and "E".
- Using DVOM, check resistance between CKP sensor connector (harness side) terminal No. 2 and engine ground. Maximum resistance is one ohm. If resistance is within specification, go to next step. If resistance is not within specification, repair open or short circuit. Erase DTC memory and test drive vehicle. If an open or short circuit cannot be located, replace faulty PCM. Code new PCM and test drive vehicle. See PCM CODING in this article.
- Using DVOM, check resistance between CKP sensor connector (harness side) terminal No. 1 and test box socket A9. Maximum resistance is one ohm. If resistance is within specification, go to next step. If resistance is not within specification, repair open or short circuit. Erase DTC memory and test drive vehicle. If an open or short circuit cannot be located, replace faulty PCM. Code new PCM and test drive vehicle. See PCM CODING and in this article.
- Using DVOM, check resistance between CKP sensor connector (harness side) terminal No. 2 and test box socket A10. Maximum resistance is one ohm. If resistance is within specification, circuit is okay. Erase DTC memory and test drive vehicle. If resistance is not within specification, repair open or short circuit. If an open or short circuit cannot be located, replace faulty PCM. Code new PCM and test drive vehicle. See PCM CODING in this article.
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When to See a Mechanic
Stop DIY work and contact a certified mechanic immediately if any of the following apply:
- • You smell fuel, burning insulation, or see smoke.
- • Brakes feel soft, pull hard to one side, or make grinding noises.
- • The engine overheats, stalls repeatedly, or misfires under load.
- • You are missing required tools, torque specs, or safe lifting equipment.
- • You are not confident in the next step or safety outcome.