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Knock sensor test 700

posted by  someone claiming to be John Sargent on  Sun Dec 2 12:44 CST 2001 [RELATED]

A recent post asked if it was possible to have a bad knock sensor which was causing the turbo to glow after operation. If the knock sensor, or it's wiring is bad, the timing will be retarded causing the engine/turbo to run hotter. Following is how to test the knock sensor with the ignition test point. Check your ignition timing before starting the test.

First you need Volvo tool 9995280-6, which is simply an LED in series with a 750 ohm resistor. The MVP site used to have instructions for making the tool. I will put the link to MVP's site at the bottom of this post. This tool is also used for checking and setting the idle mixture on the LH 2.1 and 2.2 Jetronic.

This check is good for the following ignition systems; EZ102K (B23FT), EZ 115K (B280), and EZ117K (B230F and B230FT).

Next find the ignition test point. It is a yellow/red wire, and it is one of two wires in a black plastic wiring connector on the left inner fender well quite close to the Power Stage. There is also a pink wire, and they both come out of the main wiring harness just forward of the power steering reservoir on our cars with B230FT.

Now, plug in Volvo tool 9995280-6, (or its equivalent which you have just made) to the yellow/red wire and connect the other end to the positive terminal of the battery just like if you were going to check the idle mixture. The LED should come on with the ignition. If the light does not come on there is an open circuit problem. The light will go out about 800 rpm(B23FT), 700 rpm (B280), and 920 rpm (B230F and B230FT). If the light does not go out there is a problem in the test circuitry. Operate the engine in excess of 3500 rpm for at least five seconds, and then allow the engine to run at idle. Observe the LED for at least three minutes. If there are 4 flashes, there is a problem with the knock sensor function. These problems include:

1. Knock sensor not connected

2. Knock sensor not torqued to specs

3. Open circuit between knock sensor and control unit.

4. Wires to knock sensor reversed at control unit. Green wire to pin 13, shield wire connected to pin 12 (B230F and B230FT), Green wire to pin 8, shield wire to pin 15 (B23FT), pin 12 and 24 shield-pin 13 and 25 green (B280F).

5. Defective control unit.

There are a number of other tests which can be performed, but this post is long enough. Message me is your light has different than no flashes (no problems), or the four flash test summarized here for the knock sensor function.





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