I need some help, please. My 98 C5 got a check engine light, so I rented a scanner from Autozone. I was an ASE master mechanic before I retired from fixing cars at a GM dealership in 98, so I know the diagnostic procedures involved. The scanner returned a code for one of the knock sensors, but didn't have the ABS section I was also interested in. I bought a new Scanner from Amazon that does address ABS, it says I need a left front sensor, I put that off for another time. I bought 2 new knock sensors (ACDelco) along with the new harness as recommended. The job itself was easy, and I took the opportunity to clean and paint the parts of the engine that were exposed by the work. The front knock sensor was badly corroded, and there was a lot of junk in the well, indicating a leaking seal.

After re-assembling the parts I now have TWO knock sensor codes, for both banks. I disassembled all of the connectors for cleaning and resetting the contact pin socket tension, that made no difference, the scanner shows a low voltage code for both knock sensors. Anyone out there have any ideas for a solution?

The engine runs normally, and does NOT knock or ping on any acceleration rate. In the past, when I found knock sensor codes in customer's Corvettes (prior to 98) I always heard spark knock on even mild acceleration. To rule out some of it, I cleaned and checked for continuity or resistance every connector under the hood, the ones I could get to. And I checked the connectors at the ECM, BCM, and all of the fuses in both fuse boxes. I don't have a problem with going back into the knock sensors, but an idea of what to look for would be nice.

Thanks in advance for any ideas you might have.

 

So you know you can read diagnostic codes via the DIC and a scan tool is not needed???

 

https://www.corvetteforum.com/forums...nsor-code.html

 

A GM Master Tech ???....we should be asking you for advise...LOL !!...what DTC’s did you have...0327/0332 ??
...did you check the circuit from the PCM out to the harness ??...do you have a lab scope ??...if not you can use a DVOM but as you probably know it will only average the AC voltage from the sensor...you can try giving the exhaust manifold a couple love taps while back probing the signal wire and see what the sensor is putting out i f anything...you’ll be lucky to see maybe close to .1 VAC maybe !!...I can’t remember if there is a bias voltage on that line but you can probably check that...did you ohm out the new sensors ??...I believe you’ll be looking in the K Ohms but I can’t remember the number...this is a torque for those things and it’s critical...another thing that you can check is your alternator ripple since the both the ABS sensors and knock sensors produce AC...just a thought ...I had a Forum member I know call me and said his Wife’s Tahoe was throwing both those DTC’s (knock and WSS) if I can remember...he had close to 1 volt AC ripple...a new alternator took care of that..I probably don’t think I have to tell you how to check AC ripple...good luck !!

 

Thanks, those are some good ideas to chase. I have been suspecting that the alternator isn't right, it sometimes goes over-voltage, but turning on the ac and running lights always gets it below 14.4. I did read the sensor signal at each wheel while turning the wheels, I got a low voltage but steady ac signal, the same at all wheels. Initially I had intermittent signals at all wheels, working on the harness connectors got them all steady. I had to do a search for the GM connector tool I hadn't used since 98.

 

I know knock sensors can be damaged from over torquing upon installation. But I suppose you know that as well as I.

 

Moved to C5 Tech.

 

For the doubters-


I always had ASE Certification since the 70's, but in the early 90's a service manager decided that he need at least one master in the service dept, so he sent me to Jacksonville to take the GM automatic transmission course, the only area I had very little experience in, although I had done some work on automatics. After passing that course I took the ASE exams in all areas and got the Master Certification. I mostly worked on engine, drive train, and drive-ability problems, and was given the difficult-to-fix problems for the whole shop. I retired from auto repair before the first C5 warranty problems began to show up, so I can't claim to be expert in C5 and later Vettes. I started work for Harber Chevrolet in 1972 as a Corvette mechanic, based on my experience racing my own Corvettes, 2 C2 Models. No one else in that shop was willing to touch a Vette at that time. I took numerous GM training center courses, GM sent me 'Certified technician' diplomas, I never got any explanation of what that meant. I held a 100% customer satisfaction rate for two years just before I left the Chevy dealership.

Other training was on Mazda rotary engines and manual transmissions, and Mitsubishi Engines, because the GM dealers I worked for also sold those brands. I was the only mechanic in the dealership for the additional brands. I had customers who refused to take their car into the dealership for repairs, so I also fixed cars in my garage at home, nights and weekends, until I decided, (or my Wife did) that I was doing too much. During all the time I worked for dealerships I built racing engines for others at home. My best customer raced an aluminum big block C3 in SCCA competition. I didn't build HIS engine, but I made it go, solving a misfire problem and tuning the engine. He reported over 220 mph on the back straight at Daytona, might have been exaggerating, but he let me test drive it, 95 mph in first gear. I decided to not go any faster. I built differential gears for the sports car racers, I knew how to build for endurance.

 

Not sure anyone was doubting you, just ironic you're on here asking us for advice.

Anywho, do you know how to check a knock sensor with a multimeter? I would probably check both of them and ensure they're actually giving off a voltage with knock.

 

The torque on the knock sensors is (10 in lbs.) incorrect, the correct torque is 15 ft lbs, according to the info I got in this forum. I did use anti-seize on the threads because of the corrosion I found in there, is it possible that the anti-seize is the problem?

Yes, I know how to check them, and I will when I get back into it.

 

I have never been one to think I know everything, getting advice from others can save time.

 

Torque is 15 in pounds

 

Torque is 15 FOOT POUNDS !!...or 180 INCH POUNDS if your torque wrench reads that !!...if you used 10 INCH POUNDS that is barely finger tight !!

 

15 FOOT POUNDS !!...not INCH POUNDS !!

 

That’s what I meant Lol! The point is that he said he torqued it to 10 so that’s why he’s still getting codes

 

Don't get excited, I checked the torque chart, I tightened to 15 ft lbs, the torque wrench is still set on that. The 10 inch pounds was something else, with a different torque wrench, I ain't that dumb. I got bad short term memory so I double check everything I do.

 

You also have Great sense of humor. I'm just following along. Learning.

 

I know that codes can be read at the DIC, but if it were a customer car, I wouldn't be poking their buttons with MY greasy fingers, and my car is just as important to me. The only time I was ever responsible for messing up a customer car was when my night watchdog, a 135 lb. German Shepard, climbed up on the convertible top of a really nice C1 Vette, to nap in comfort in his new hammock. Fortunately for me, this happened back when you could get them for a reasonable price. We had set up a barricade to keep him out, he tore through.

 

??
Are you aware of the TSB GM issued concerning the knock sensor DTC's ??...don't know if you did the RTV thing on installation per the TSB...BTW, did you ever get this patch on your arm ??...what percentage of dealer Techs had it ???




Audible Spark Knock (Detonation), MIL Illuminated, DTC P0332 Set (Replace Rear Bank Knock Sensor and RTV Area Around Sensor) #02-06-04-023
Audible Spark Knock (Detonation), MIL Illuminated, DTC P0332 Set (Replace Rear Bank Knock Sensor and RTV Area Around Sensor)
1998-2002 Chevrolet Camaro, Corvette
1998-2002 Pontiac Firebird

with 5.7L Engine (VIN G -- RPO LS1)

1999-2002 Chevrolet and GMC C/K Pickup and Utility Models (Avalanche, Silverado, Sierra, Tahoe, Suburban, Yukon, Yukon XL, Yukon Denali, Yukon Denali XL)

with 4.8L, 5.3L or 6.0L Engine (VINs V, T, Z, N, U -- RPOs LR4, LM7, L59, LQ9, LQ4)

Condition
Some customers may comment on a mild to severe engine ping (commonly referred to as spark knock), usually worse during acceleration and/or an illuminated MIL. Upon investigation, the technician may find DTC P0332 set.

Cause
This condition may be the result of corrosion of the rear bank knock sensor due to water intrusion into the sensor cavity. This condition is more apparent on vehicles in which customers frequently wash the engine compartment.

Correction
Replace the rear bank knock sensor and build a dam (wall) around the sensor using RTV to divert water away from the sensor. Use the procedure and part number listed below.

Remove the intake manifold. Refer to the Intake Manifold Replacement procedure in the Engine Controls sub-section of the appropriate Service Manual.

Remove the wiring harness assembly from the knock sensor.

Remove the rear bank knock sensor.
Install the new rear bank knock sensor. Tighten
Tighten the knock sensor to 20 N·m(15 lb ft).

Install the wiring harness assembly to the knock sensor.

Apply a bead of RTV silicone sealant approximately 9 mm (3/8 in) wide and 6 mm (1/4 in) high along the outside edge of the ridge on the engine block valley cover around the rear bank knock sensor. DO NOT form a complete circle. Leave the rear section open as shown.
From the underside of the intake manifold, completely remove the rear intake manifold seal (foam material).
Install the intake manifold. Refer to the Intake Manifold Replacement procedure in the Engine Controls sub-section of the appropriate Service Manual.
Parts Information
Part Number
Description
Qty

10456603
Sensor, Knock
1


Parts are currently available from GMSPO.

Warranty Information
For vehicles repaired under warranty, use:

Labor Operation
Description
Labor Time

J4437

(F-Car)
Sensor, Knock -- Replace
1.7 hrs

Add

(1998-1999 F-Car Only)
To Remove EGR
0.2 hr

J4437

(Y-Car)
Sensor, Knock -- Replace
1.6 hrs

J4437

(C/K-Truck)
Sensor, Knock -- Replace
1.5 hrs

Add

(C/K Truck Only)
With Three Piece Engine Covers
0.2 hr

Add

(All)
Diagnosis Time
0.3 hr

Add

(All)
To RTV Area Around Sensor and Remove Intake Manifold Seal
0.2 hr

 

First question is where did you buy the replacement sensors, I bought a pair of "genuine AC Delco with harness" from Fleabay looked correct, from the plastic bag packaging to the markings on the sensor body. Drove for about 50 miles and codes came right back, pulled the manifold and sensor one of the sensors tested open, returned to seller, purchased AC Delco from Rockauto and problem solved. What I'm saying is there are so many counterfeits out there and you can't tell them from the real parts.
Good luck