95 Chevy (Knock Sensor/Service Engine Soon)

userpete1037 · #1 03-21-2007, 01:54 PM

I replaced the knock sensor and now the service engine soon light has come on and hasn't gone off. I should tell you that i didn't disconnect the negative battery cable before installation as the manual says. Would this have anything to do with it?

2000CAYukon · #2 03-21-2007, 04:56 PM

Use a paper clip to find what code (or codes) is stored. See http://www.troublecodes.net/GM/ for details on how to read the codes with a paper clip.

//2000CAYukon

userpete1037 · #3 03-22-2007, 08:20 PM

Tried the paper clip but didn't get any results. I took it to a local part store to get a diagnostic test ran on it but they didn't have a scanner to hook up to it. Something about if it was a 96 model, they could do it. Although the manual doesn't say it, I'm wondering if the sensor has to be tightened to a specific torque? I know it's working because i have no more pinging in my truck. I even drove it up a steep hill to see. That service engine light is just damn aggrevating!!!!

2000CAYukon · #4 03-22-2007, 08:25 PM

Quote:

Originally Posted by userpete1037

Tried the paper clip but didn't get any results.

Can you be more specific? Did you have the ignition on but not running the engine? Did you jumper between A&B? Did the Check engine light flash at all when you did this?

//2000CAYukon

userpete1037 · #5 03-22-2007, 09:45 PM

Ignition was on but not running, jumped A&B and no flash whatsoever.

userpete1037 · #6 04-04-2007, 08:22 PM

Okay, i purchased a code scanner for my truck and it spit out codes: 32 and 43. According to the manual, Code 32: Barometric pressure sensor circuit failure OR EGR valve closed during start-up or open when EGR flow requested by ECM OR EGR/EVRV. Code 43: EST circuit - low voltage detected or ESC - circuit problems.

Can anyone tell where to start. I'm not sure if the EGR valve is bad or what? What i do know is, before I replaced the knock sensor, my service engine light would come on every once in a while. All i had to do was restart the truck and it would shut off. Now it's just on whenever i start the truck.

PLEASE HELP/ADVISE!!!!!!

abaird · #7 04-04-2007, 09:34 PM

With the engine running try to push on the diaphram in the EGR valve this should open the valve and the engine should start to sputter or idle low. If it doesn't, or the valve is stuck then you have a problem with the valve or EGR passages. The ECM will only ask for EGR flow when you are at operating temp and at cruising speeds so if the valve isn't working you will get a check engine light at those conditions. When you set timing on these older vehicles that still use a distributor to control timing, you have to go into EST bypass mode by disconnecting an electrical connector and this will set a code. Thats what that code 43 sounds like. Clearing codes on pre 96 vehicles is as simple as disconnecting the battery.

userpete1037 · #8 04-04-2007, 11:41 PM

okay, thanks for the response. I will try that this weekend and post thread afterwards.

2000CAYukon · #9 04-05-2007, 01:01 PM

You can push the EGR to check if it stuck; however, it also has to hold vacuum to work properly. You need a vacuum pump to test the EGR. With the engine off, apply around 20 in-HG of vacuum to the EGR valve (not the solenoid). It should hold the vacuum. If not, replace the EGR valve. If it holds, start the engine. The vacuum should drop to zero, if not replace the EGR valve.

To test the solenoid, apply vacuum to the TBI side of the solenoid. It should hold vacuum, if not replace solenoid. If it holds vacuum, connect PINs A and B of the ALDL connector (see www.troublecodes.net/GM for details) with the ignition on, and the vacuum should drop to zero (note disconnect the EGR side of the solenoid for this test).

Also make sure the vacuum hoses are in good shape since a vacuum leak on either hose can set the Check Engine Light.

//2000CAYukon

userpete1037 · #10 04-05-2007, 10:16 PM

Well I pushed the diaghram of the EGR valve in and the engine did sputter and idle low. However, I guess I need to vacuum test it and the solenoid to be sure. Where can I get a vacuum and is it expensive?

2000CAYukon · #11 04-05-2007, 11:08 PM

Quote:

Originally Posted by userpete1037

Well I pushed the diaghram of the EGR valve in and the engine did sputter and idle low. However, I guess I need to vacuum test it and the solenoid to be sure. Where can I get a vacuum and is it expensive?

Now you know that the EGR is not stuck. I paid around $50 for the vacuum pump at a local parts store. I use it a lot so it was worth the money to me.

Something like http://www.partsamerica.com/ProductD...egoryCode=3412

//2000CAYukon

userpete1037 · #12 04-06-2007, 08:05 PM

Okay, I'm confused a little bit and If you read further i guess you will see why. I purchased a vacuum pump attahched it to the EGR solenoid valve applying 20 in-HG and it held vacuum just fine. Here's where i get confused. In one of my previous statements, I depressed the diaphram of the EGR by hand and the engine sputtered...etc..etc. However, I connected the vacuum pump to the EGR valve and applied vacuum and nothing changed in the idling or running of the engine. How is that when I depressed the EGR valve by hand, it changed the idling of the engine. Does this mean that the EGR valve is bad?

klinn · #13 04-07-2007, 09:20 PM

When you connect the vacuum pump to the EGR (where the vacuum line connects), it should pump up and hold vacuum. If it doesn't the EGR diaphram has a leak, and the EGR valve will need to be replaced. As far as the knock sensor replaced without battery disconnected, don't worry about that. After you test/repair the EGR system, disconnect the battery for a couple of minutes, that SHOULD reset the check engine light and clear any codes set by diagnosing and or repairs you have done in the past. Then if the check engine light comes on again. You shouldn't have any additional codes to confuse you. Hope this helps.

userpete1037 · #14 04-10-2007, 05:55 PM

I replaced the EGR valve and the service engine soon came back on after about 30 secs or so. I re-scanned the vehicle and the code 32 has been elimated which i assume the new EGR valve did that. Now I only have the code 43 which I assume has something to do with the ECM or new knock sensor. According to my repair manual, the knock should have a resistance of 100K ohm and mines is at 99.6K ohm which i guess is fine even though i dropped it by mistake before putting it on.

PLEASE ADVISE......

bamadam · #15 04-10-2007, 10:20 PM

Quote:

Originally Posted by userpete1037

I replaced the EGR valve and the service engine soon came back on after about 30 secs or so. I re-scanned the vehicle and the code 32 has been elimated which i assume the new EGR valve did that. Now I only have the code 43 which I assume has something to do with the ECM or new knock sensor. According to my repair manual, the knock should have a resistance of 100K ohm and mines is at 99.6K ohm which i guess is fine even though i dropped it by mistake before putting it on.

PLEASE ADVISE......

99.6K is close enough. Did you disconnect the battery to clear the codes?? Sorry if I missed that.

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