95 burb code 43 knock sensor

[jimh]

'95, 350, 2 wheel drive - I'm getting SES with code 43. I replaced the knock sensor and the "single wire" and connector seem to be in good shape. The wire disappears into a wiring harness, then into a heat-shield tube connected to the bell housing. I don't know where that wire goes after that. Straight to the ECM? I've searched around and I still don't know how this sensor works. Haynes manual says it should supply a 8-10 volt signal when no knock is detected. Where does the voltage come from if there is only 1 wire?

Anyway, since it's running sluggish, I believe that the ECM is retarding the timing as it is supposed to (I think). What is the best way to test this connection, where is the other end of the dark blue wire, is this the voltage I should be looking for, etc.???

Also, the water pump is squeeling pretty bad. I am replacing that tonight. Is it possible that the sensor is picking up that noise and making the ECM think that there is a ping going on? Just a thought.

p.s. I hear no pinging, but then again, the water pump could be drounding it out.

Thanks in advance to all that will help me.
Jim

[MT-2500]

Originally Posted by jimh

'95, 350, 2 wheel drive - I'm getting SES with code 43. I replaced the knock sensor and the "single wire" and connector seem to be in good shape. The wire disappears into a wiring harness, then into a heat-shield tube connected to the bell housing. I don't know where that wire goes after that. Straight to the ECM? I've searched around and I still don't know how this sensor works. Haynes manual says it should supply a 8-10 volt signal when no knock is detected. Where does the voltage come from if there is only 1 wire?

Anyway, since it's running sluggish, I believe that the ECM is retarding the timing as it is supposed to (I think). What is the best way to test this connection, where is the other end of the dark blue wire, is this the voltage I should be looking for, etc.???

Also, the water pump is squeeling pretty bad. I am replacing that tonight. Is it possible that the sensor is picking up that noise and making the ECM think that there is a ping going on? Just a thought.

p.s. I hear no pinging, but then again, the water pump could be drounding it out.

Thanks in advance to all that will help me.
Jim

Knock sensor wiring goes into VCM/PCM.
Best way to test is to watch the reading on a good engine capable scanner.
Tap on the block or head and you sould see it kick in and retard timing.
MT

[777stickman]

Please clarify, since you replaced the knock sensor are you still getting the code 43???

A worn out squeelling water pump can really drag an engine down HP wise and possibly send a signal to the knock sensor.

[jimh]

OK, I have replaced the knock sensor and am still getting code 43, after clearing all codes. I have also replaced the water pump since it was making some noise and had a little play in the shaft.
Since this a '95, I don't think it has a PCM under the hood. It seems that all the timing is controlled by the knock sensor to ECM (with 8 -10 volts if no knock detected) and then the ECM retards the timing if no voltage.
I'm still confused where the voltage comes from if there is only 1 wire on the knock sensor?!?
Anyway, I am working on it again this weekend. I'm starting with my voltmeter connected directly to the knock sensor and ground to see if I am getting any voltage. It sounds like I have to take the glove box out to get to the ECM. Haynes manual says that this sensor should be coming in on terminal B7. We'll see.
I'll update after more poking around.
Thanks for your input and keep it coming if you have any more ideas.
Jim

[MT-2500]

Depends on if you have spark control or dual or signal knock sensors.

Signal and dual knock sensors with out spark control.
You should have a 5 volt signal on pcm wiring at pin B-15 with knock sensors unpluged.
With sensors hocked up they should pull the B-15 pin line voltage down to 2.5 volts.

A knock or tapping on block should change B-15 line voltage under or over 2.5 volts.
B-15 may be a dark blue wire.

[jimh]

Thanks for the reply MT. That makes more sense to me that the voltage doesn't come from the sensor, but the sensor can pull the voltage down. It is a dark blue wire at the sensor. I have only found a single knock sensor, on the lower block, passenger side.
I'll reply back with progress.
Jim

[jimh]

Well, correct, 5 volts at dark blue wire to sensor when not connected to sensor. Connect blue wire to "new sensor" and still 5 volts. Take out new sensor and put "old sensor" back in. Voltage drops to 2.5 like you said it should.
So unless the noisy water pump was confusing things, I don't know what caused the error code in the first place. Also, although the new and old sensors look the same, do some act different. If there are no differences in how the sensors effect the voltage, looks like I bought a defective sensor.
So far, no new error codes. Getting ready for a test drive now.

Thanks for the help.

p.s. This '95 350 appears to have the single knock sensor with the Electronic Spark Control (ESC) mounted near the throttle body.

Thanks again.
Jim

[MT-2500]

Originally Posted by jimh

Well, correct, 5 volts at dark blue wire to sensor when not connected to sensor. Connect blue wire to "new sensor" and still 5 volts. Take out new sensor and put "old sensor" back in. Voltage drops to 2.5 like you said it should.
So unless the noisy water pump was confusing things, I don't know what caused the error code in the first place. Also, although the new and old sensors look the same, do some act different. If there are no differences in how the sensors effect the voltage, looks like I bought a defective sensor.
So far, no new error codes. Getting ready for a test drive now.

Thanks for the help.

p.s. This '95 350 appears to have the single knock sensor with the Electronic Spark Control (ESC) mounted near the throttle body.

Thanks again.
Jim

You are welcome.
Voltage check on old sensor sounds good.
What is the engine code?
TBI or Multi port fuel injection?

That may be the knock sensor module / ESC spark controller.


If so the voltage checks and repair flow charts are different.

If knock signal wire th pcm is B-7 then it has esc spark control
If the signal feeds to B-15 on pcm it is without ESC electronic spark control.


Doe it run good with no codes on the old knock sensor?

A lot of times code 43 is caused by wiring or knock sensor plug in.
Check the plug in on sensor real good.
Let us know how it goes.
MT

[jimh]

Code 43 has not reappeared yet, knock on wood. This has the ESC with 1 knock sensor. TBI.

So, it idles smoother now and seems to have better acceleration, not so sluggish. I post if anything goes south.

Thanks for the help,
Jim