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.
1987 Volkswagen Quantum Base, StandardFACTORY OEM SERVICE PROCEDURE
Knock Sensor
- With ignition off, disconnect knock sensor from control unit. Measure resistance between terminals No. 13 and 14. Type I sensor should have 300K ohms resistance. A Type II sensor should measure infinity. Reconnect sensor to control unit.
- Connect LED Test Light (US 1115
) to single lead (Brown) connector and to battery (+) voltage. LED must light.CAUTION: DO NOT use a standard test light to test knock sensor. Higher voltage type light may damage control unit.
- With engine running, LED should go out (may glow slightly). Increase engine RPM one time to 3000 RPM. If LED lights again connect a jumper wire between outside terminals of knock sensor connector and momentarily (3 seconds) ground (-) center terminal.
- The LED light will blink on and off in a pattern. Blinking twice at intervals indicates a fault in the knock sensor (sensor defective, wiring, mounting torque) or defective control unit.
- If the LED light blinks three times in intervals it indicates a break in the vacuum hose to the control unit or the control unit vacuum sensor is defective.
Factory Service Tools
Use the Manual With the Right Hardware
Pair factory procedures with proven DIY tools so the instructions are easier to execute.
Disclosure: Verified tool recommendations may earn an affiliate commission at no cost to you.
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.
Rather have a pro handle this?
A certified mobile mechanic comes to your home or office. They bring the tools, you stay comfortable. No tow truck, no waiting room, no surprises.
Comes to youSame-day available12-month warranty
Get a Free QuoteNo obligation. See pricing before you book.