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2001 5.3 silverado extra cab
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Discussion Starter · #1 ·
So, I did the typical repair,
New AC DELCO OEM knock sensors and short harness. Cleaned everything up, had water in back port, did the TSB related work, adding circular dams of silicon. Torqued properly. The truck has not seen rain or any other water since repair…

I drove it around town about a month and thought I was home free. But NOPE. I hooked up my boat and hopped on interstate for a 450 mile run…about 2 miles down highway the light came on, codes 332 & 327! I had my code reader, reset it about 3 of 5 stops along the way, sometimes I could run 150 miles (2.5 hours) with no code. Since I have returned, it throws codes every time I drive it.
I have checked connections, fuses, etc.

the truck runs great, 160k 2001 5.3 silverado extra cab…all stock.

I am going to test the voltages, got questions.
what’s the normal reading/range?
does a knock cause a high or low reading?
I am 99% sure my codes are LOW voltage…so maybe a bad ground?

The one issue I have that I wonder if it’s causing a knock reading?? A Few of my fuel injectors are really noisy, very audible in the cabin of the truck. I mean so loud it sounds like a diesel engine, a normal person would think my truck is diesel powered. I know it’s the fuel injectors, I used a stethoscope to go over the entire engine, the only place I picked up the sound was on fuel rail and injectors….super quiet everywhere else. Just trying o rule things out, my injectors sound like a badly knocking engine….

So how does a knock sensor work, does it just pick up rattlle or knock, change voltage to tell the computer to adjust timing air fuel to eliminate the knock? Is a knock a drop or increase in voltage?

I have also seen the sensor relocation kits, anyone have success with that or other solutions????

I would ignore this but in GA they will fail my annual inspection and refuse to renew my tag….
 

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1999 Silverado ECSB 6.0
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Check your motor mounts. My knock was because the engine was rocking too much.
 

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The knock sensor picks up vibration and sound coming from the engine block, turns it into an electronic signal and sends that signal to the engine control unit (ECU). The car's computer then judges the information and determines whether or not ignition timing should be altered.

If ur injectors are that bad, then yes replace them. Go with factory stock OEM units.
 

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So, I did the typical repair,
New AC DELCO OEM knock sensors and short harness. Cleaned everything up, had water in back port, did the TSB related work, adding circular dams of silicon. Torqued properly. The truck has not seen rain or any other water since repair…

I drove it around town about a month and thought I was home free. But NOPE. I hooked up my boat and hopped on interstate for a 450 mile run…about 2 miles down highway the light came on, codes 332 & 327! I had my code reader, reset it about 3 of 5 stops along the way, sometimes I could run 150 miles (2.5 hours) with no code. Since I have returned, it throws codes every time I drive it.
I have checked connections, fuses, etc.

the truck runs great, 160k 2001 5.3 silverado extra cab…all stock.

I am going to test the voltages, got questions.
what’s the normal reading/range?
does a knock cause a high or low reading?
I am 99% sure my codes are LOW voltage…so maybe a bad ground?

The one issue I have that I wonder if it’s causing a knock reading?? A Few of my fuel injectors are really noisy, very audible in the cabin of the truck. I mean so loud it sounds like a diesel engine, a normal person would think my truck is diesel powered. I know it’s the fuel injectors, I used a stethoscope to go over the entire engine, the only place I picked up the sound was on fuel rail and injectors….super quiet everywhere else. Just trying o rule things out, my injectors sound like a badly knocking engine….

So how does a knock sensor work, does it just pick up rattlle or knock, change voltage to tell the computer to adjust timing air fuel to eliminate the knock? Is a knock a drop or increase in voltage?

I have also seen the sensor relocation kits, anyone have success with that or other solutions????

I would ignore this but in GA they will fail my annual inspection and refuse to renew my tag….
Hello,

You might consider checking the resistance of the new sensors to make sure they weren't bad out of the box. Resistance should be 93-107K ohms. According to the repair information I have, the torque is also important on these knock sensors, and both should be snugged down to 15 ft lbs. There's also a TSB (02-06-04-023A) that indicates the rear bank knock sensor is susceptible to water intrusion (when you go through a car wash, etc.). Beyond that, you'll want to start looking at the rest of the circuit for both knock sensors.
 

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^^^^Yeppers.^^^^ I R&R the ones on my '99 4.8L with all OEM parts without incident.

But if his injectors are truly that noisy, me thinks the damn thing shouldn't even run! LOL
The new sensors may be picking up the pintle vibrations from both banks, confusing the confuser/computer. Seems like a far stretch but may be possible.....

Perhaps a wiring diagram and a multi-meter would be in order to chase the wiring to the confuser to check wire integrity. Connector terminals can fret or corrosion hidden inside them.
 

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2001 5.3 silverado extra cab
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Discussion Starter · #7 ·
My knock sensors came in small plastic bags, rolling around the inside of the box from Rock Auto…there was typical air bag packaging…I will test them with an olm meter once it quits raining here…
 

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2001 5.3 silverado extra cab
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Discussion Starter · #8 ·
UPDATE, still have codes. I took my multimeter down and disconnected connector at the rear of the intake. I measured 99.5 to 99.7 fairly consistently with stable connection to knock sensor lead and firewall ground. I inspected all wire bundles for cuts, breaks, cracks and any evidence of rodents, found none. Wiggled all grounds and wire bundles….stable…So what’s my next step? I consistently get P0327 & P0332 together at the same time. From this test it appears the knock sensors and short harness are good. Thanks!
 

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2001 5.3 silverado extra cab
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Discussion Starter · #9 ·
Hello,

You might consider checking the resistance of the new sensors to make sure they weren't bad out of the box. Resistance should be 93-107K ohms. According to the repair information I have, the torque is also important on these knock sensors, and both should be snugged down to 15 ft lbs. There's also a TSB (02-06-04-023A) that indicates the rear bank knock sensor is susceptible to water intrusion (when you go through a car wash, etc.). Beyond that, you'll want to start looking at the rest of the circuit for both knock sensors.
Thanks, FYI, read TSB before repair, did cleaning, drying of water, new intake gaskets, silicone water dam, all new AC DELCO parts and harness. Measured 99.7 ohms today on both sensor leads At back of intake junction.
 

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^^^^Yeppers.^^^^ I R&R the ones on my '99 4.8L with all OEM parts without incident.

But if his injectors are truly that noisy, me thinks the damn thing shouldn't even run! LOL
The new sensors may be picking up the pintle vibrations from both banks, confusing the confuser/computer. Seems like a far stretch but may be possible.....

Perhaps a wiring diagram and a multi-meter would be in order to chase the wiring to the confuser to check wire integrity. Connector terminals can fret or corrosion hidden inside them.
Agreed. At this point, I would suggest purchasing a single-vehicle subscription to an online repair database and following the diagnostic flowchart for the codes (and consulting the wiring diagram). Or you might consider having a professional repair shop take a shot at diagnosing the problem. You can find links to a couple of recommended repair databases here if you decide to go that route.
 

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2004 Sierra 3500 6.0L, auto, extended cab, cab&chassis, upgraded to 4wd
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...note, alldatadiy has jacked up prices over the last year or two. Now alldatadiy is up to $60/year or $130/3 years (from $50/5 years)... Mitchell doesn't seem to have yet.
 

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2001 5.3 silverado extra cab
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Discussion Starter · #12 ·
I guess it’s time to head down to local shop for diagnostic, they charge $79? For advanced diags? I wonder if I could do the same with an advanced OBDII reader? I just have simple one. when my P0446 would not go away they determined I had low voltage from fuel pressure sender, I could not see that…..

I have read ECM might be bad but I have no other codes….any idea on price to program one? I can buy one on Rock Auto for under $200….
 

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2001 5.3 silverado extra cab
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Discussion Starter · #13 · (Edited)
So it took the truck in for advanced diagnostics. They can’t find anything wrong other that the code for under voltage on both knock sensors. Asked a million questions, they insist it’s bad sensors, even though olm meter reads 99.7 for each. So I got warranty replacements for the knock sensors. Will try the process again. Truck is becoming a money pit of electrical issues, like every other chevy I owned…
 

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2001 5.3 silverado extra cab
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Discussion Starter · #14 ·
The knock sensor picks up vibration and sound coming from the engine block, turns it into an electronic signal and sends that signal to the engine control unit (ECU). The car's computer then judges the information and determines whether or not ignition timing should be altered.

If ur injectors are that bad, then yes replace them. Go with factory stock OEM units.
So my question is: does a knock cause Voltage to increase or decrease? ( I have loud injector rattles and knock sensor low voltage errors)
 

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So it took the truck in for advanced diagnostics. They can’t find anything wrong other that the code for under voltage on both knock sensors. Asked a million questions, they insist it’s bad sensors, even though olm meter reads 99.7 for each. So I got warranty replacements for the knock sensors. Will try the process again. Truck is becoming a money pit of electrical issues, like eve other chevy I owned…
I wonder what the shop did beyond pulling codes? Oddly enough, it seems that torque is very important when installing these knock sensors. I suggest carefully torquing them to spec this time around if you didn't do so the first time. If the second set of sensors doesn't fix the problem, there's likely circuit problem that will need to be tracked down.

The sensor creates an AC signal that increases in frequency in response to knocking. Here are a couple of good videos on knock sensor operation and testing:


 

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2001 5.3 silverado extra cab
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Discussion Starter · #17 ·
Thanks for reply, yes carefully torqued to specs, new everything, yes new harness just like that. truck did not see any moisture before code came back. I am about to tear it out and replace it all again in the next few hours. Did the TSB for preventing water, etc..by the book repair after lots of research….
 
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2004 Sierra 3500 6.0L, auto, extended cab, cab&chassis, upgraded to 4wd
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Maybe test the resistance at the other end of the wires, at the connector plugging into the ecm? Perhaps there is some corrosion on a connector or even in the wires somewhere.
 

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2001 5.3 silverado extra cab
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Discussion Starter · #19 ·
Maybe test the resistance at the other end of the wires, at the connector plugging into the ecm? Perhaps there is some corrosion on a connector or even in the wires somewhere.
Yeah, I would not be surprised if it’s wiring between the ECM and the sensor. I don’t have a wiring diagram..I did inspect everything I could see for chaffing and rodent damage and corrosion. The fuse block was clean and dry….I put new sensor in again today, now I wait….
 

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Discussion Starter · #20 ·
So just to follow up, I replaced the knock sensors again with brand new set, got rid of those codes, and immediately got a “too lean” warning. I could not find any air leaks around intake and problem self healed. Now I have contastand “cargo light on” warnings. It’s not on, and interior courtesy lights are dead. (Fuses are good).
something tells me my BMC is flakey, maybe my ECU also…. I can’t find any bad grounds.

the joys of owning a GM product. Electrical gremlins.
 
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