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Knock Sensor Testing and Replacement
 
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Pelican Technical Article:

Knock Sensor Testing and Replacement

Nick Czerula

Time:

4 hours4 hrs

Tab:

$200

Talent:

*****

Tools:

Set of sockets (10, 12mm), flathead screwdriver, DVOM

Applicable Models:

Volvo V70 (1998-01)
Volvo V70 2.4T (2001)
Volvo V70 AWD (1998-99)
Volvo V70 GLT (1998-00)
Volvo V70 GLT SE (2000)
Volvo V70 R (1998)
Volvo V70 R AWD (1999-00)
Volvo V70 T5 (1998-01)
Volvo V70 X/C (2001)
Volvo V70 X/C AWD (1998-00)
Volvo V70 X/C AWD SE (2000)

Parts Required:

Knock sensor

Hot Tip:

Work with a cool engine

Performance Gain:

Remedy knock sensor fault codes

Complementary Modification:

Replace breather hoses and crankcase breather

Engine knock or detonation in spark-ignition internal combustion engines occurs when combustion of the air and fuel in the cylinder starts off correctly in response to ignition by the spark plug, but one or more pockets of air explode outside the area of the normal combustion front, causing a shock wave and a collision, resulting in the knocking sound. The shock wave creates the characteristic metallic pinging sound, and cylinder pressure increases dramatically. Effects of engine knocking range from non-damaging to completely destructive.

Pre-ignition in an engine is the event wherein the air / fuel mixture in the cylinder ignites before the spark plug fires. Pre-ignition is caused by an ignition source other than the spark plug, such as hot spots in the combustion chamber, a spark plug that runs too hot, or carbon deposits in the combustion chamber.

V70 5-cylinder normally aspirated engines utilize one sensor to monitor engine knock. The knock sensor is mounted to the engine block, beneath the intake manifold. The knock sensor usually fails setting a check engine light and a knock sensor fault code, such as P0325 knock sensor circuit. When a knock sensor fails, the ignition timing on your engine may be held in a retarded position until the fault is remedied, therefore reducing engine power and the chance of detonation. The sensors are replaced in pairs and you have to replace the fasteners also. In this tech article I will go over how to test and replace the engine knock sensor on your Volvo V70 with a normally aspirated engine.

Remember that your car may have been serviced before and had parts replaced with different size fasteners used in the replacement. The sizes of the nuts and bolts we give may be different from what you have so be prepared with different size sockets and wrenches.

Protect your eyes, hands and body from fluids, dust and debris while working on your vehicle. If you're working with the electrical system, disconnect the battery before beginning. Always catch fluids in appropriate containers and properly dispose of any fluid waste. Recycle parts, packaging and fluids when possible. Never work on your vehicle if you feel the task is beyond your ability.

Our vehicle may vary slightly from yours as models do change and evolve, as they grow older. If something seems different, let us know and share your info to help other users. Do you have questions or want to add to the article? Leave a comment below. When leaving a comment, please leave your vehicle information.

This photo shows the location of the knock sensor (red arrow).
Figure 1

This photo shows the location of the knock sensor (red arrow). Disconnect the negative (-) battery cable. See our tech article on battery connection notes. Remove the intake manifold. See our tech article on intake manifold removing.

To replace the knock sensor, disconnect the electrical connector (red arrow).
Figure 2

To replace the knock sensor, disconnect the electrical connector (red arrow). Start by sliding the connector off the housing toward the left (green arrow).

Press the release tab (red arrow) and pull the electrical connector apart.
Figure 3

Press the release tab (red arrow) and pull the electrical connector apart.

Working at the knock sensor, remove the 12mm knock sensor fastener (red arrow).
Figure 4

Working at the knock sensor, remove the 12mm knock sensor fastener (red arrow).

Then remove the knock sensor from your engine.
Figure 5

Then remove the knock sensor from your engine. Fish the sensor wiring from behind the starter motor (red arrow).

Be sure the mounting surface is clean (red arrow).
Figure 6

Be sure the mounting surface is clean (red arrow). Then install the new knock sensor finger tight. Then torque the knock sensor fasteners 20 Nm. Reassemble the engine and check the DME for fault codes.

Testing knock sensors: To test the sensors, you will have to access the knock sensor electrical connector.
Figure 7

Testing knock sensors: To test the sensors, you will have to access the knock sensor electrical connector. Working at the electrical connector, you will backprobe the connector with the ignition ON. There are two wires at the connector. One is a ground. The other is a reference voltage used for circuit integrity. Here's the quick test. Use a DVOM. Connect the black lead to battery negative. Then connect the positive lead to the black sensor wire (red arrow). This is the ground and should be zero volts (yellow arrow). Then backprobe the brown wire (blue arrow). This should read around 2.5 volts for a good sensor (green arrow). A bad sensor will either short the reference voltage to ground, or not pull it down to 2.5, therefore giving a reading of about 5 volts.

Testing knock sensors: You can also test the ECM side of the harness for the right voltage.
Figure 8

Testing knock sensors: You can also test the ECM side of the harness for the right voltage. Use a DVOM, connect the black lead to battery negative. Then connect the positive lead to the black sensor wire (red arrow). This is the ground and should be zero volts. Then backprobe the brown wire (green arrow). This should read around 5 volts (yellow arrow). You can also test resistance of the sensor. The specification is 200k Ohms.


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