Page 1 of 2 12 LastLast
Results 1 to 20 of 22

List of Sensors and What They Do

This is a discussion on List of Sensors and What They Do within the General Help forums, part of the LSx Technical Help Section category; Basic LS1 components Firing order: 1-8-7-2-6-5-4-3 The firing order of the LS1/Vortec V8 has been revised from the Gen I ...

  1. #1
    None Shall Pass Knight's Avatar
    Join Date
    Jan 2010
    Location
    East of Cleveland, Ohio
    Posts
    3,831

    Black
    99 WS.6 - Modified

    List of Sensors and What They Do

    Basic LS1 components

    Firing order: 1-8-7-2-6-5-4-3

    The firing order of the LS1/Vortec V8 has been revised from the Gen I and Gen II engines. This was done to provide more power, less crankshaft rotational stress and better emission and idle qualities.

    Camshaft sensor (CMP)

    The camshaft sensor is a 1X pulse sensor which is synchronized to the #1 firing of the engine (Whether or not it is on its firing or exhaust stroke). The reluctor is located on the back of the camshaft. As the reluctor rotates, it interrupts the magnetic field produced by the sensor and the pcm interprets this as a pulse, after the signal is buffered by the internal circuitry of the CMP. The pcm uses this signal in conjunction with the crankshaft sensor (CKP) to determine the crank position and stroke. The pcm monitors this signal for any problems and sets the appropriate DTC (diagnostic trouble code) for loss or degraded signal. The pcm provides the +12V power, ground and signal return for the CMP.

    A loss of this signal will result in longer starting times. The location of the CMP is on the top rear center of block.

    Crankshaft sensor (CKP)

    The crankshaft sensor is a 24X pulse sensor that controls ignition coil firing and injector pulse. The 24 tooth reluctor wheel is mounted on the back of the crankshaft. This location is known as the "quiet" deflection zone that minimizes any false signals to the pcm that can be misinterpreted as a fault. As with the CMP, the crankshaft sensor is a magnetic sensor that has the field interrupted by the passing of the teeth on the reluctor. This signal is conditioned by the sensor circuitry so it can be properly used by the pcm.

    The pcm constantly times the pulse intervals it receives, in conjunction with the CMP to resync the point of the #1 firing stroke. Any changes to the timed intervals at each firing order stroke is read by the pcm as a change in crankshaft velocity. Using the other sensors such a MAP, and TPS, the pcm can determine the changes in crankshaft speed when the engine is accelerating or decelerating, within normal operating conditions, and when the changes are outside the normal parameters, the pcm detects this as a misfire, and the appropriate DTC is set.

    A loss of this signal will result in a no-start condition. The location of the CKP is on the right hand side above the starter.

    Knock sensors (KS1 and KS2)

    The LS1 engines use two knock sensors, the part number is the same for both, but they have two distinct wires to the pcm. The front sensor (KS1) monitors the first 4 cylinders (2 each left and right) while the KS2 monitors the back 4 cylinders. Based on information from the crankshaft sensor, the pcm can detect which cylinder is firing, and each cylinder that is causing a knock situation. The information broken down into a trouble code can tell the technician which cylinder is not receiving fuel, or spark, or is under knock conditions.

    Location for the sensors is on the top of the block under the intake.

    Intake Air Sensor (IAT)

    Depending on the type of MAF sensor, the IAT can be either located in the air intake tract or internal to the MAF sensor. The LS6 uses the 85mm MAF that has the IAT integral to the sensor.

    The IAT (which is also the same as the MAT on older Fuel Injected engines) uses a thermistor which changes resistance based on the air temperature entering the engine. The normal range is from 100K ohms @ -39F, to 70ohms at +266F. At room temperature, this can be from 1500 to 2500 ohms.

    The pcm supplies a 5V signal to the sensor and monitors the signal on the return. This voltage variation is used by the pcm along with the MAF to determine air density and therefore alter the spark timing accordingly.

    When the engine is completely cooled down, the scan tool should read a temperature close to the ambient air temperature. When the engine is started and running, the temperature should rise as under hood temperature increases.

    Engine Coolant Temperature (ECT) sensor

    The ECT, like the IAT is a thermistor sensor, so it also changes the resistance based on temperature. The same range of resistance (ohms) is used as in the IAT. The pcm also sends a 5V signal to the sensor and monitors the return voltage. When the engine has not been run for several hours, the scan tool should read the IAT and ECT temperatures close to each other.

    The PCM uses the signal for many of the control systems that affect fuel economy, emissions and idle, so any degraded or loss of signal has a great impact on the engine performance.

    There are two different ECT sensors. One is a three wire used on very early (1997-98) LS1 engines, where the third wire (usually green) goes directly to the temperature gauge on the instrument panel. The later engines use a two wire sensor and the pcm conditions the signal and a separate signal from the pcm goes to the gauge on the instrument cluster.

    The ECT location is in the front of driver's side cylinder head.

    Manifold Absolute Pressure (MAP) sensor

    The MAP sensor is used to measure the amount of pressure change inside the intake manifold. When the vacuum signal is high (idle and deceleration) the voltage is low, while under load and acceleration, when the vacuum signal is low, the voltage from the MAP sensor is high. Just remember that the MAP is inversely proportional to what is measured with a vacuum gauge. This signal is used for the following operations:

    Altitude compensation
    Ignition timing control
    Speed density fuel management default (MAF sensor failure).

    Location of the LS1/LS6 MAP sensor is located on rear of the intake manifold.

    Mass Air Flow (MAF) sensor

    The MAF sensor is used to measure the amount of air entering the engine. Idle conditions equal a low air flow, and engine under acceleration indicates a high air flow. The pcm uses the MAF to determine the amount of fuel delivery to the engine.

    The MAF sensor has a ignition +12V power source, a ground and signal return. The sensor is a hot wire type that the MAF frequency output is a function of how much power it takes to keep the sensing wire at a preset temperature above the ambient temperature. Air flowing across the heated sensing wire cools the wire, and the current increases to maintain this preset temperature. The current increase or decrease is proportional to the air flow. The MAF sensor converts this current into a frequency which is read by the pcm and calculates the air flow in grams per sec (gm/sec). The scanner should display around 9-14 gm/sec, on a fully warmed up engine at idle.

    The pcm monitors this voltage to determine if the MAF is performing properly and sets the appropriate DTC based on this information.

    There are two types of MAF sensors. One is he 75mm used on the early LS1 engines, which is a three wire type, and the 85MM version used on the LS6 which has the integral IAT sensor (5 pin sensor).

    Throttle Position (TP) sensor

    Like the older engines, the TP (or TPS) is mounted on the throttle body throttle shaft. The sensor is a potentiometer that varies the voltage output based on position (in this case, the angle of the throttle blade). At idle, the output voltage is around 0.6V, and at WOT this voltage is around 4.0V. The pcm sees the signal, along with the CMP, CKP, MAP and MAF to determine if the engine is accelerating or not. This affects many systems, including emission system and fuel calibration control. An erratic or faulty TP sensor will cause erratic engine performance. A DTC will be set depending on the type of fault condition the pcm sees.
    Last edited by Knight; 08-19-2011 at 05:17 AM.

  2. #2
    None Shall Pass Knight's Avatar
    Join Date
    Jan 2010
    Location
    East of Cleveland, Ohio
    Posts
    3,831

    Black
    99 WS.6 - Modified

    Throttle Bodies

    There are 4 common throttle bodies used on the Gen III engines, two of which are used on the LS1. The most common will be the cable style throttle body used on the F-body LS1 from 1998 through 2002. The other is DBW (Drive by Wire). The cable driven throttle body is a mechanical throttle body actuated by a cable linked to the accelerator setup. The DBW throttle body is an electronically actuated throttle body which receives signal from a potentiometer on the accelerator pedal.

    Idle Air Control (IAC) Valve.

    The IAC is a pcm controlled stepper motor located in the throttle body, just above the TP sensor. The IAC has pintle that moves back and forth controlling idle speed based on temperature and external loads imposed on it such as the alternator output and AC compressor load. Basically the IAC bypasses air from the outside through a opening just behind the throttle blades. Thus, it acts as a "controlled vacuum leak". The pintle moves away from its seat, to bypass more air and increasing idle speed ( on cold engine start up, or when loads are added that would cause the engine to stall), and moves toward its seat, decreasing the amount of bypass air and lowering idle speed (with engine warming up).

    The pcm moves the pintle in steps, called "counts". The higher the number, the higher the idle speed and lower counts result in decreased idle speed. The idle speed is determined on:

    Battery voltage
    Coolant temperature
    Engine load
    Engine rpm ( as determine by the CKP)
    If the rpm drops below specification with the throttle closed, the pcm will increase the pintle position and calculate this in its memory to prevent stalling. Engines speed is a function of total air intake into the engine (IAC pintle position + throttle angle + bypass air + calibrated vacuum loss through accessories).

    The controlled idle speed is programmed into the pcm and the correct IAC position is determined for all engine operating parameters. The minimum air rate is set at the factory with a stop screw. This setting allows just enough air to bypass the throttle blade to cause the IAC pintle to be positioned in a calibrated number of steps.

    NOTE: Do not attempt to adjust idle speed by turning the screw on top of the right side of throttle body, you will damage the IAC motor.

    Vehicle Speed Sensor (VSS)

    The VSS is an important sensor used by the pcm to determine how fast the vehicle is moving. Located at the back end (tailshaft) of the transmission on either the automatic (4L60E) or manual (T56), this sensor is basically a signal generator that puts out an AC signal that the voltage also increases proportional to how fast the vehicle is moving. The reluctor in the transmission is a 40 tooth wheel. The VSS can be miscalibrated by not using the factory calibrated tire size and gear ratio that was originally installed with the vehicle. Any LS1 retrofit into another vehicle will certainly mean that the pcm will have to be recalibrated for the new tire size and/or gear ratio.

    Ignition Control (IC)

    The ignition control for the LS1 consists of the following systems:

    One ignition coil for each cylinder
    Separate IC control circuit for each coil
    CMP
    CKP
    PCM

    To control the proper firing order of the ignition coil, the pcm bases the information of the following:

    Engine load based on MAP sensor signal
    Air intake based on MAF signal input
    Intake air temperature
    Crankshaft position
    Engine speed (RPM)
    The 24X signal from the CKP not only determines the firing of the ignition coils, but the firing of the injectors as well. The pcm ground the circuit of the IC and this triggers the ignition coil to fire. The timing is not adjustable.

    Each cylinder has its own coil. The early 1997-98 LS1 engines with perimeter valve cover bolts had the coils mounted directly to the valve cover, later engines that used the center bolt covers has coil mounting brackets.

    O2 Sensors

    The O2 sensors on the LS1 are used to monitor the oxygen content in the exhaust gasses. The optimum mixture is to keep to close as a 14.7 to 1 ratio as possible. The LS1 engines use 4 sensors, 2 on each side, one ahead of the catalytic converters, the other one is called the post catalytic sensor. The first sensor in the stream ahead of the converter is use to trim the fuel calibration to keep the emissions to a minimum, the post-cat sensor is to monitor the efficiency of the converter. The first sensor swings from about .250V to .900V, adjusting from rich to lean detection. The post-cat sensor should have barely any voltage swing at all, if it does, it means the catalytic converter is defective and not cleaning up the exhaust. Any deficiency in any sensor will set a DTC.

    Most retrofits will not use the post-cat sensor if legal to do so, but the pcm will have to be reprogrammed to ignore the two post cat sensors or a SES light will come on and a code will be thrown. The first two sensors will have to be retained.
    Last edited by Knight; 08-19-2011 at 05:20 AM.

  3. #3
    None Shall Pass Knight's Avatar
    Join Date
    Jan 2010
    Location
    East of Cleveland, Ohio
    Posts
    3,831

    Black
    99 WS.6 - Modified


  4. #4
    None Shall Pass Knight's Avatar
    Join Date
    Jan 2010
    Location
    East of Cleveland, Ohio
    Posts
    3,831

    Black
    99 WS.6 - Modified

    If anyone has any other sensors that I may have forgotten, please feel free to list them and a description of their location.

  5. #5
    Paid off 1/27/14 cammed goat's Avatar
    Join Date
    Jan 2009
    Location
    Paterson/Ridgewood, NJ
    Posts
    11,198

    Phantom Black Metallic
    2004 GTO M6

    I like this thread. Still reading it...and it has been schtuck.

  6. #6
    Moderator Cutlass's Avatar
    Join Date
    Apr 2008
    Location
    Madison, WI
    Posts
    6,854

    1999 Formula WS6 M6-sold
    2001 Silverado Z71

    Excellent info!!

  7. #7
    Moderator 35th-ANV-SS's Avatar
    Join Date
    Oct 2008
    Location
    Wherever life takes me
    Posts
    11,356

    Red
    02 35th LE Camaro SS

    Great write-up Walt. Subscribed for future reference.

  8. #8
    None Shall Pass Knight's Avatar
    Join Date
    Jan 2010
    Location
    East of Cleveland, Ohio
    Posts
    3,831

    Black
    99 WS.6 - Modified

    Thanks guys. It doesn't seem quite as complicated of a setup now, at least to me. Hopefully it's helpful.

  9. #9
    Moderator Cutlass's Avatar
    Join Date
    Apr 2008
    Location
    Madison, WI
    Posts
    6,854

    1999 Formula WS6 M6-sold
    2001 Silverado Z71

    The more you know, the easier it gets

  10. #10
    She Moderator KahanaReef's Avatar
    Join Date
    Jul 2008
    Location
    So Cal
    Age
    50
    Posts
    14,771

    Arctic White
    2000 Camaro

    Awesome write up, Walt! Thanks for putting that together

  11. #11
    Junior Member
    Join Date
    Jan 2012
    Location
    Ashland, Ohio
    Posts
    8
    Subscribed, this is just what I was looking for! Thanks for posting..

  12. #12
    Member pop6482's Avatar
    Join Date
    Oct 2010
    Location
    Wilkes-Barre Pa.
    Posts
    128

    Red/Black
    1989 Camaro IROC

    Good stuff. Thanks!
    1989 IROC: 6.0 LQ4/T56, Torquer V2, PRC Stage 2.5 5.3L Heads, FAST 78mm TB, SPEC stg. 2, Stainless Works LT's, e-cutout, magnaflow, subframe connectors, lca's, panhard, torque arm, strut tower bar

  13. #13
    None Shall Pass Knight's Avatar
    Join Date
    Jan 2010
    Location
    East of Cleveland, Ohio
    Posts
    3,831

    Black
    99 WS.6 - Modified

    Glad it helps!

  14. #14
    Member SS Camaro UK's Avatar
    Join Date
    Sep 2011
    Location
    England
    Posts
    159

    Black on Black
    2002 Camaro SS

    Just out of curiosity, is the EVAP canister purge solenoid something that can be removed and deleted, like the AIR system?

  15. #15
    Junior Member aviationphotog's Avatar
    Join Date
    May 2008
    Location
    trophy club, texas
    Posts
    18

    silver
    2002 SS Camaro

    anyone one know where to by 02 sensor extentions for the front ??

  16. #16
    None Shall Pass Knight's Avatar
    Join Date
    Jan 2010
    Location
    East of Cleveland, Ohio
    Posts
    3,831

    Black
    99 WS.6 - Modified

    I wouldn't recommend extensions, as they've been known to cause issues. Most people go with the Bosch 13111's. They have extra long harnesses, and will work perfectly.

  17. #17
    Spaz is My Mentor SMWS6TA's Avatar
    Join Date
    Feb 2009
    Location
    Ugy Lower Corner of AL
    Posts
    7,734

    Navy Blue Metallic
    98 T/A - LQ Power!!!!

    Quote Originally Posted by SS Camaro UK View Post
    Just out of curiosity, is the EVAP canister purge solenoid something that can be removed and deleted, like the AIR system?
    Yes you can but the CCP code has to be removed from the tune, block off the vacuum port on the intake and remove the hose and canister (located on drivers rear wheel area)

  18. #18
    Moderator Cutlass's Avatar
    Join Date
    Apr 2008
    Location
    Madison, WI
    Posts
    6,854

    1999 Formula WS6 M6-sold
    2001 Silverado Z71

    If you get rid of the purge solenoid, you might as well trash the vent valve and canister as well. Leave a vent hose uncapped or put a breather on it so you can fill the tank. You garage will most likely smell like gas fumes.

  19. #19
    Spaz is My Mentor SMWS6TA's Avatar
    Join Date
    Feb 2009
    Location
    Ugy Lower Corner of AL
    Posts
    7,734

    Navy Blue Metallic
    98 T/A - LQ Power!!!!

    Cut, does getting rid of help in HP gains or is it so minimal that it doesn't matter?

  20. #20
    Moderator Cutlass's Avatar
    Join Date
    Apr 2008
    Location
    Madison, WI
    Posts
    6,854

    1999 Formula WS6 M6-sold
    2001 Silverado Z71

    No HP gains. Just visual improvement and weight reduction. But it's very minimal. Not worth it to me to have gas fumes in the garage.
    -------------------------------------
    Kooks 1 7/8" race headers, Kooks ORY, Borla catback, Nitto 555R, LS6 intake manifold, Shaner S3 ported stock throttle body, SLP lid, smooth bellows, JAAM Ram Air kit, Elite Engineering catch can, LS6 valley cover, EGR and AIR deleted, Frost tune, and Simpson Racing child car seat in the back. 13.2 @ 108MPH

Page 1 of 2 12 LastLast

Thread Information

Users Browsing this Thread

There are currently 1 users browsing this thread. (0 members and 1 guests)

Bookmarks

Posting Permissions

  • You may not post new threads
  • You may not post replies
  • You may not post attachments
  • You may not edit your posts
  •