Code 22

braaap11889 · #1 08-15-2006, 09:22 AM

So I just found out why my check engine light is on its a code 22 ( Knock sensor 1 (RH)) What does that mean the definition on svx-iw.com is Abnormal voltage in knock sensor monitor circuit

So what im understanding is the knock sensor (don't know what that is) not getting the right signal

Thats all I understand my dad might understand more but he probably won't know what to do to fix it

So thats what I'm here asking about What does the trouble code mean is it bad? I have driven about 300 miles with it like that so I hope im not wrecking my car its a 1992 svx with exactly 135005 miles on it

How can I fix it? What do I need to buy and where is the sensor? And any other common questions that I forgot I wouldn't mind having answered

Thanks

Jared

Mr. Pockets · #2 08-15-2006, 10:22 AM

Trouble codes don't specifically tell you a sensor is bad - it's possible that the wiring harness is at fault, for example. That's why it tells you the fault is coming from that circuit, and not just the sensor.

In all likelihood, you have a bad knock sensor and need to replace it. I've never replaced one, so I don't know how much the part costs.

Earthworm · #3 08-15-2006, 11:09 AM

That's the easy sensor to replace however a lot of people will tell you to replace both sensors at the same time.

When I replaced both of mine the plastic housings were both cracked/broken.

b3lha · #4 08-15-2006, 01:07 PM

The service manual says that when you get Code 22 then you should check the knock sensor and it's wiring. The resistance of the knock sensor should be approximately 560k Ohms. The wire should be at 2-3 volts when the ignition is on. So that is absolutely the first thing to check. I'll add some further info from my personal experience. But take it with a grain of salt because I can't find anything to support this in the service manual.

The knock sensor detects vibrations from the engine that indicate that it is knocking. When the ECU gets a signal from the knock sensor it retards the ignition timing until the knocking stops.

Some time ago I picked up a load of really bad fuel in my 94. The car wouldn't run on it. I had to drain the fuel tank, but obviously I couldn't get every last drop out so there was still a certain amount of bad fuel mixed in with my first tank of good fuel.

For that first tankfull, I was occasionally getting codes from one or other of the knock sensors. I think that the engine was knocking due to the bad fuel. The ECU was retarding the timing to try and stop the knock, but the knocking didn't stop so perhaps the ECU decided that the sensors must be bad. It wasn't obvious to me that the engine was knocking. It just sounded maybe a little less smooth than usual, difficult to say for sure. After the next fill up everything was OK.

In summary, I think another possible undocumented cause of this code is that your engine is knocking due to fuel/timing issues and the ECU is assuming the sensor to be bad because it cannot stop the knocking.

If the knock sensors and their wiring test out OK then try filling up with premium fuel and resetting the ECU.

subru92svx · #5 08-15-2006, 06:20 PM

My check engine light came on in my svx around 110,000 miles and thats what the code was for mine to was knock sensors. I replaced both of them at the same time. At a cost of around $200.00-$250.00 I believe. It took me about two-three hours since it was my first time. When I got them out and looked at them they were both cracked. One sensor is in the front of the motor that you can see if you look in the space between alternator and ps pump. It lies about 4 inches back underneath intake manifold.To get to the front one remove your alternator and it makes it very easy to reach. Then the second one is towards the back and to the right side you can see it looking into the engine compartment from drivers side. This one you don't need to remove anything it is just a very tight fit and harder to get to.There is only one bolt holding each sensor in place. Try to place the new sensors the same way the old ones were sitting is what I was told by the dealer. The tools I used to get to them and get them out was a 1/4 inch ratchet, three extensions, a universal joint, and a 10 and 12 mm socket. Make sure you do not over torque the new ones and crack them. Hope this helped some.

Trevor · #6 08-15-2006, 06:57 PM

Quote:

Originally Posted by b3lha

The service manual says that when you get Code 22 then you should check the knock sensor and it's wiring. The resistance of the knock sensor should be approximately 560k Ohms. The wire should be at 2-3 volts when the ignition is on. So that is absolutely the first thing to check. I'll add some further info from my personal experience. But take it with a grain of salt because I can't find anything to support this in the service manual.

The knock sensor detects vibrations from the engine that indicate that it is knocking. When the ECU gets a signal from the knock sensor it retards the ignition timing until the knocking stops.

Some time ago I picked up a load of really bad fuel in my 94. The car wouldn't run on it. I had to drain the fuel tank, but obviously I couldn't get every last drop out so there was still a certain amount of bad fuel mixed in with my first tank of good fuel.

For that first tankfull, I was occasionally getting codes from one or other of the knock sensors. I think that the engine was knocking due to the bad fuel. The ECU was retarding the timing to try and stop the knock, but the knocking didn't stop so perhaps the ECU decided that the sensors must be bad. It wasn't obvious to me that the engine was knocking. It just sounded maybe a little less smooth than usual, difficult to say for sure. After the next fill up everything was OK.

In summary, I think another possible undocumented cause of this code is that your engine is knocking due to fuel/timing issues and the ECU is assuming the sensor to be bad because it cannot stop the knocking.

If the knock sensors and their wiring test out OK then try filling up with premium fuel and resetting the ECU.

I would take that said with a lot more than a grain of salt. The analysis is logical and valid.

The knock sensors contain a ceramic element and are quite fragile in respect of heat and age, so that failure must be suspect.

Beav · #7 08-15-2006, 07:40 PM

Knock sensors operate by generating a voltage signal. The ECU expects to 'see' a certain voltage with the key on, engine off and a varying range of frequency and amplitude while the engine is running. If either situation fails, either by way of defective circuitry or sensor, the code will set.

Phil, I would hazard to guess that was a relearn issue rather than a result from bad fuel. The ECU had been adapting/updating to changing values as the sensor went belly-up. When you changed the sensor it had to adapt itself back into the range of the new sensor - a process that doesn't occur very rapidly. The programmers don't want a code setting because of mechanical issues, which could cause knocking that wouldn't be rectified by timing adjustment, that's the reason for my doubt.

Resetting the ECU is not a magic cure for anything except an errant spike that might keep the car from running at all. What does happen is that the adaptive values are lost and the engine will run far from optimum until a number of 'drive cycles' are completed and the values are relearned. As our cars age, more and more of the sensors will have gained more resistance, which affects their static values. It takes longer each time the ECU is reset for the values to be relearned as there probably isn't a single sensor with a value close to prime. Values are relearned as a result of cross-referencing look-up tables at specific times. If none of the sensors are at base-line to begin with it's a difficult proposition. Resetting doesn't cause damage (other than a loss of performance/mpg during the relearn process) but it doesn't cure anything either.

Trevor · #8 08-15-2006, 08:40 PM

Quote:

Originally Posted by Beav

Knock sensors operate by generating a voltage signal. The ECU expects to 'see' a certain voltage with the key on, engine off and a varying range of frequency and amplitude while the engine is running. If either situation fails, either by way of defective circuitry or sensor, the code will set.

Phil, I would hazard to guess that was a relearn issue rather than a result from bad fuel. The ECU had been adapting/updating to changing values as the sensor went belly-up. When you changed the sensor it had to adapt itself back into the range of the new sensor - a process that doesn't occur very rapidly. The programmers don't want a code setting because of mechanical issues, which could cause knocking that wouldn't be rectified by timing adjustment, that's the reason for my doubt.

Resetting the ECU is not a magic cure for anything except an errant spike that might keep the car from running at all. What does happen is that the adaptive values are lost and the engine will run far from optimum until a number of 'drive cycles' are completed and the values are relearned. As our cars age, more and more of the sensors will have gained more resistance, which affects their static values. It takes longer each time the ECU is reset for the values to be relearned as there probably isn't a single sensor with a value close to prime. Values are relearned as a result of cross-referencing look-up tables at specific times. If none of the sensors are at base-line to begin with it's a difficult proposition. Resetting doesn't cause damage (other than a loss of performance/mpg during the relearn process) but it doesn't cure anything either.

Greetings Beav,

The actual point was that Phil did not have a sensor problem as such and all was confined to bad fuel. He had not in fact changed a sensor as you suggest. Easy to have read too quickly and be deceived by following on from the previous posts for sure.

But so what, your post provides valuable information.

Keep it coming, Trevor.

Beav · #9 08-15-2006, 09:04 PM

Oops, you're absolutely correct. I did run the posts together in my head. Trying to read too much, too fast.

I've not run into a car that the knock sensors would trigger in that manner but I seriously doubt I'll ever see everything, let alone understand it if and when I do.

I do know the knock sensors on the SVX closely resemble the ones used on Nissan and since Subaru sources many items from Nissan I wouldn't doubt they are identical. It's no secret that Nissan's knock sensors almost always display trouble codes when accessing scan data and replacing them rarely supplies a cure. I'll watch their response on a graphing meter during a 'tap test' and if they respond I leave them alone. The programming or the sensor design must be an issue for them and makes me curious if the SVX's sensors are not the same. Since mine have never pitched a code I can't check them. And you know me, I don't trust resistance checking as an accurate or revealing method of testing for very many items...

Trevor · #10 08-16-2006, 12:26 AM

Quote:

Originally Posted by Beav

Oops, you're absolutely correct. I did run the posts together in my head. Trying to read too much, too fast.

I've not run into a car that the knock sensors would trigger in that manner but I seriously doubt I'll ever see everything, let alone understand it if and when I do.

I do know the knock sensors on the SVX closely resemble the ones used on Nissan and since Subaru sources many items from Nissan I wouldn't doubt they are identical. It's no secret that Nissan's knock sensors almost always display trouble codes when accessing scan data and replacing them rarely supplies a cure. I'll watch their response on a graphing meter during a 'tap test' and if they respond I leave them alone. The programming or the sensor design must be an issue for them and makes me curious if the SVX's sensors are not the same. Since mine have never pitched a code I can't check them. And you know me, I don't trust resistance checking as an accurate or revealing method of testing for very many items...

OK Beav and no ooooops called for,

I agree on the resistance check not being effective. You are dealing with what amounts to a crystal/ceramic/piezo electric phonograph pick up, driven by a weighted actuator so as to have only a limited, selective response, but high output and which generates a voltage into a relatively high impedance input. A fixed internal resistance is included in parallel, so that checking the resistance can in no way prove that the element is active and generating a voltage. The static 2-3 volts present will come from the input circuit which must be some form of crude amplifier, possibly OP amp based so as to record a difference rather than amplitude..

Probably both Subaru and Nissan purchase from the same specialised manufacturer. Same part different label.

Now I see that I have written a sort of lecture out of interest in the subject raised. I hate to think that I may be giving the impression of blowing trumpet.

Please excuse.

Cheers, Trevor.

b3lha · #11 08-16-2006, 02:59 AM

Beav, you know far more about this stuff than I ever will.

I merely posted my observation that bad fuel produced knock sensor codes for my car. As Trevor kindly pointed out, I did not replace the sensors and the problem went away after the next fill up.

My suggestion to reset the ECU was intended to clear any values learned from running on bad fuel, if indeed that was Jared's problem. It's more likely that he has a faulty sensor.

Phil.

braaap11889 · #12 08-21-2006, 01:12 PM

Cleaned the engine compartment it was off all of a sudden drove about 150 miles and started it up this morning engine light is back on

Realtyem · #13 02-10-2007, 07:44 AM

...the check engine light comes on and you take it to the dealer. The dealer says it's the knock sensors after hooking up the diagnostic tool(didn't tell me what error code it was). He says it will take a week to order the parts, and I can drive the car around til then. When I get it back, there is NO check engine light on. Does that mean that they aren't as bad as he said they are?

I was under the impression that if the sensor was bad it would still be bad even after they reset the diagnostic unit and the light would still be on.

Perhaps a bad gas symptom like above(I don't believe this to be, I've only used premium)? I'm not looking forward to spending like $800 to fix something that doesn't need to be fixed. Anybody lend some insight to this? Thanks in advance.

Trevor · #14 02-10-2007, 02:56 PM

It would appear that he has reset the fault indication and a fault has not again been indicated. He will be presuming that you have an intermittent fault. It will be interesting to see if indication returns given more time.

Beav · #15 02-10-2007, 04:01 PM

As I stated above, these appear to be the same sensors that Nissan (including Mercury Quest) uses on their V6 engines. I have yet to scan one that didn't have a knock sensor code. You can clear the code and it will return sporadically, but inevitably. I've replaced a number of Nissans and can't recall a single one that the new sensor didn't leave a code within a week or two. So.... now when I see the code I do a 'tap test' to see if the sensor actually works. If it responds properly I leave it alone. I don't even bother clearing the code anymore. IMHO it's probably a software error, engineered to too tight of an expected response range.