knock sensor codes
Thread Starter
Instructor
Joined: Dec 2015
Posts: 156
Likes: 8
From: Florence South Carolina
knock sensor codes
Just finished a build and took car to a repetable tuner yesterday. I noticed the cars rpms would surge from 800 to 300 rpms when letting off the gas over and over again preparing to stop. The car wouldn't stall out, and when the car actually stopped, the rpms would kevel back out to 800 rpm. I thought it was odd, but not really knowing any better I assumed it must be from the size of the cam. Drove 150 miles back from tuner, no engine light. Today, after driving 2 miles engine light came on pcm P0327 H C & P0332 H C.
My question from what I've read, surging could cause these faults. Did I get a ****** tune ?
My question from what I've read, surging could cause these faults. Did I get a ****** tune ?
Last edited by appliance guy; Jun 1, 2016 at 10:32 PM.
Melting Slicks
Joined: Feb 2001
Posts: 2,803
Likes: 358
From: Northville, MI
Those are knock sensor codes, check and see of the builder put sealer around the two sensors in the engine block. Checking requires the removal of the intake and looking for some silicone sealer around the two sensors. If not moisture/oil has penetrated the seal and fouled the sensors. If you have to replace them I would recommend GM parts and a new wire harness as well. This was a common problem on the 99-2007 truck engines and they had a TSB on it.
Melting Slicks
Joined: Jun 2002
Posts: 2,152
Likes: 241
From: Northern VA
I'm going through the same thing. I've put in a LS-7 and I had to move my knocks to the side of the block (no provision for valley install in an LS-7) and I'm having the same idle issues. I've been told that these KS's can be super sensitive especially in a modded motor and that a tuner can desensitize them. I'm planning on having that done shortly.
Tech Contributor
Joined: Dec 1999
Posts: 32,910
Likes: 2,402
From: Anthony TX
CI 6,7,8,9,11 Vet
St. Jude Donor '08
The Knock sensors are under the intake manifold they connect to a wire harness that sets below the intake manifold and connects to a connector at the back of the block:
97-2000 C5 set up:
2001+ set up:
Single Wire connection below the cap:
Sensor with connector removed:
IMHO,, You should pull the intake manifold and inspect the sensor wells for oil/water, inspect the wires, and make sure that they are not damaged.
YES, the tuner can desensitize the sensors output or change the PCM settings to be less sensitive to the misfire count...
97-2000 C5 set up:
2001+ set up:
Single Wire connection below the cap:
Sensor with connector removed:
IMHO,, You should pull the intake manifold and inspect the sensor wells for oil/water, inspect the wires, and make sure that they are not damaged.
YES, the tuner can desensitize the sensors output or change the PCM settings to be less sensitive to the misfire count...
Le Mans Master
Joined: Aug 2005
Posts: 5,375
Likes: 328
From: CA.
St. Jude Donor '13-'14-'15
As Bill mentioned yes a tuner can desensitize the knock sensors But only have that done IF you don't hear any audible pinging--other wise it will ping even more !!
The idle surging and bucking is common on most all cam installs---Not a fault of the tuner as often the car has to be driven for 50-75 miles to let the trims settle down and the idle to learn out--After some driving the tuner can make the adjustments after the learn out--otherwise he is simply guessing and chasing his tail
PS---surging can be caused by many thing on a cammed car
Most often :
add air to the "desired airflow table" in the idle section
add 3-4 * of timing to the "base timing in gear and in P/N"
Make sure at idle and mid part throttle all your fuel trims are "slightly negative OR 0"
corrected using your MAF table
The idle surging and bucking is common on most all cam installs---Not a fault of the tuner as often the car has to be driven for 50-75 miles to let the trims settle down and the idle to learn out--After some driving the tuner can make the adjustments after the learn out--otherwise he is simply guessing and chasing his tail
PS---surging can be caused by many thing on a cammed car
Most often :
add air to the "desired airflow table" in the idle section
add 3-4 * of timing to the "base timing in gear and in P/N"
Make sure at idle and mid part throttle all your fuel trims are "slightly negative OR 0"
corrected using your MAF table
Thread Starter
Instructor
Joined: Dec 2015
Posts: 156
Likes: 8
From: Florence South Carolina
Car has been driven 200 miles since tune. Surging got a little better, but coasting down speed I feel isn't right. Also, once the car is up to temp and I turn it off, its more difficult to crank, like it flooded or something. I have appointment with tuner again tomorrow.
Le Mans Master
Joined: Aug 2005
Posts: 5,375
Likes: 328
From: CA.
St. Jude Donor '13-'14-'15
Coasting down RPM's is most often caused by
Too much desired airflow in the "in gear" tables if it's hanging
OR too much taken out of the "throttle follower" in gear
Again when the engine is started dead cold or started after warmed the fueling is commanded by the ECM's "open loop normal table" Typically with cams or LT headers the commanded fuel in open loop becomes too rich---So you have to command a muxh leaner AFR in open loop in order to get back to the stock open loop AFR's On my car a 98 hds/cam/hdrs-- I had to command an open loop AFR of 16.10 in order to trick the ECM back to stock open loop AFR's of 14.68--This is all a trial and error procedure that is easi;y done using a data logger with a real time dynamic testing function Either HP or EFILIVE only
Too much desired airflow in the "in gear" tables if it's hanging
OR too much taken out of the "throttle follower" in gear
Again when the engine is started dead cold or started after warmed the fueling is commanded by the ECM's "open loop normal table" Typically with cams or LT headers the commanded fuel in open loop becomes too rich---So you have to command a muxh leaner AFR in open loop in order to get back to the stock open loop AFR's On my car a 98 hds/cam/hdrs-- I had to command an open loop AFR of 16.10 in order to trick the ECM back to stock open loop AFR's of 14.68--This is all a trial and error procedure that is easi;y done using a data logger with a real time dynamic testing function Either HP or EFILIVE only
