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Old 11-08-2005, 11:31 AM
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Default What are all the Sensors on this car and what do they do? PART II


Ignition Module-Part number-25527221, AC Delco number-D1996
Diagnostic Alarm Code-42 C3I electronic spark timing (EST) failure
Location-The ignition module is located at the back of intake manifold under the coil pack.

Purpose-The ignition module controls the ignition coil pack.
How it works-The ignition module contains the primary circuits that turn the individual coils on and off. The module also controls all ignition function under 400 RPM.
Ignition Coil Pack-Part number-25533542,
AC Delco number-D552
Location-The ignition coil pack is located at the back of intake manifold on top of the ignition module.

Purpose-To deliver spark to the cylinders.

How it works-The coil pack receives a signal from the ignition module. Then it sends spark to both the cylinder and the waste spark cylinder.
Quick Check-An ohm test can determine if your coil pack is starting to malfunction. The individual towers should ohm 11k-13k, the lower the better. This is not a conclusive test. The coil pack still may be bad. The only way to check it correctly is with a CCCI Ignition Tester from Caspers Electronics.

Knock Sensor-Part number-10456287,
AC Delco Part number-213-325
Location-The knock sensor is located on the driver’s side block above the bell housing.

Purpose-The knock sensor tells the ECM if there is any detonation occurring in the engine.

How it works-It is basically an electronic microphone. It picks up frequencies and sends them to the ESC.

Torque-14 ft-lbs
Manifold air temperature sensor-
Part number- AC Delco number-213-190
Location-The manifold air temperature sensor (MAT) is located on the elbow between the MAF and the air cleaner. If a aftermarket air filter is used it normally is located beside the hose clamp.

Diagnostic alarm code-25 manifold air temperature circuit (high temp)

Purpose-The MAT relays the temperature of the incoming air to the ECM.
How it works-The ECM sensor sends out a 5 volt reference signal to the MAT sensor. The ECM will then read the resistance it receives from the MAT. If the temperature is low it will have a high reading. If the temperature is high it will receive low reading.
Mass air flow sensor- Part number-25007866 (Discontinued)
Location-The mass air flow (MAF) is located between the alternator and the radiator. One end of the MAF connects to the air filter and the other end connects to a hose/tubing that is connected to the turbocharger.

Diagnostic alarm codes- 33 MAF circuit (high)
34 MAF circuit (low or no signal)

Purpose-The MAF tells the ECM how much air the engine is using.
How it works-The MAF has a heated film that sits in the air stream. As the air passes over the film the temperature will drop. A resistor measures the temperature of the film and sends the information to the ECM.

Alternatives-The stock MAF sensors are not manufactured by GM. Some people have some luck with aftermarket rebuilt units. It seems that there is a 50% chance of the aftermarket MAF will work. Another alternative is buying a Translator. A Translator will allow you to run a later model style MAF. The most common MAFs used with the Translator is a 3” LT1 (part # 25180303), a 3.5” LS1 (part # 25179711), or a 3 5/8 Z06 (part # 25168491). Caspers Electronics sells a harness that adapts the 5 pin LS1 and Z06 MAF connector to a LT1 3 pin. This harness also integrates the air temperature sensor. This way you don’t have to run an external air temperature sensor. It is incorporated into the LS1 and Z06 MAF sensors. Full Throttle Speed & Style also sells a Translator Plus. The Plus has all of the features of the Translator. But it also let the owner adjust the ignition timing. There is also an option with the Translator that lets you double the air flow grams that the ECM sees. You have to get the Extender chip to use this option. Another alternative is a MaxEffort Digital Fuel Management system. They make a racing version of the system called ME-R. It does not use a MAF at all.
Websites-Translator-Full Throttle Speed & Style Web Site- Store Front Page
Harness-Caspers Electronics - Quality Engineered Electronic Performance Items
Maxeffort-MAXEFFORT Digital Programmable Fuel Management
Throttle Position Sensor-Part number-25036663,
AC Delco Part number-213-918
Location-The throttle position sensor (TPS) is located on the passenger side of the throttle body.
Diagnostic alarm codes-21 TPS circuit (high) and 22 TPS circuit (low)

Purpose-The TPS lets the ECM know what position the throttle shaft is located.

How it works-The ECM will send out a 5-volt reference signal. Once the ECM receives a .40-.44 volt from the TPS it knows it is at an idle. The standard setting for full throttle has always been 4.5 volts. However the ECM sees 75% of the 5 volts (3.75 volts) it will invoke power enrichment mode. The ECM has to see 4 volts to turn off the Air Conditioning. Steve Wood has a very good explanation that is a lot more in depth on his website Vortex Buicks.

Website- Vortex Turbo Buick Performance
Oxygen Sensor-Stock part number-25162693,
GNX part number-25162753
AC Delco number-213-503,
AC Delco GNX-213-504
Diagnostic alarm code-13 oxygen sensor circuit open

Location-The oxygen sensor (O2 sensor) is located on the passengers side exhaust manifold under the turbocharger.

Purpose-The O2 sensor tells the ECM if the engine is running rich or lean.
How it works-It does not make a good tuning device. If the O2 sensor sees that the air/fuel ratio is higher the 14.7, it will lean out the motor. If the O2 sensor sees that the air/fuel ratio is less than 14.7, it will give the engine more fuel.

Alternatives-For many years a lot of people changed from the stock 1 wire O2 sensor to a 4 wire heated O2 sensor. Caspers Electronics sells a plug and play wiring kit for a heated sensor. Using leaded racing fuels was one of the main reasons this was done. Denso (part number 234 0001) has come up with a new O2 sensor that is more tolerant of racing fuels. It seems to last longer than stock and heated O2 sensors. However in time the lead will clog up the sensor. Another alternative is a MaxEffort Digital Fuel Management system. It uses a thumbwheel to program the chip. MaxEffort keeps the ECM in an open loop, so an O2 sensor is not needed.

Website-MAXEFFORT Digital Programmable Fuel Management
PROM Chip-Part number-16051877,
California number-16036503
Diagnostic alarm code-51 PROM error

Location-The programmed read only memory (PROM) chip is the big computer chip located under the PROM access cover in the ECM.

Purpose-The PROM chip tells the ECM what to do.
How It Works-All of the fuel codes, ignition curves, TCC, etc are stored in the Prom chip. This is read only information, the ECM can not rewrite any of the information..
Torque Converter Clutch Solenoid-Part number-8639900
Location-You must remove the transmission pan. The TCC is located in the front of the transmission right behind the pan rail. Just follow the wires.

Purpose-The TCC sends the signal to lock the torque converter in overdrive.
How It Works- When signaled by the ECM the TCC will move the lock-up valve in the transmission. This will reverse the flow of transmission fluid and create pressure to lock the torque converter clutch up
Vehicle Speed Sensor-Part number-25007463,
AC Delco number-213-110
Diagnostic alarm code-24 vehicle speed sensor circuit failed

Location- There is two parts of a vehicle speed sensor (VSS). The first part is the reader, it is attached to the back of the speedometer. The second part is behind the stereo and heater controls. They are connected with a ribbon of three wires.

How it works-The VSS has a reader that is connected to the back of the speedometer. There are two reflective tabs on the back of the speedometer that the reader will count. Every turn of the speedometer cable results in two pulses. There are 2000 pulses in a mile. The reader will send the pulses to the module. The module will then decipher the pulses and send the information to the ECM. It is also used for cruise control.
Wastegate Solenoid-Part number-1997157,
AC Delco Part number-214-609
Location-The wastegate solenoid is located on the top of the passenger valve cover. It uses a red connector.

Diagnostic alarm code-31 wastegate solenoid electrical signal failed.
Purpose-The wastegate solenoid is how the ECM controls boost.

How it works-It is an electronic bleeder that uses a pulse width moduluation of the solenoid to bleed off boost pressure, thus keeping the wastegate flapper closed (more duty cycle) or to allow boost pressure to open the wastegate flapper (less duty cycle) to reduce boost.
Ken Mosher
1987 GN original owner 650+ HP Black
2015 BMW 328xi XDrive wagon
2012 Volkswagen Tiguan (the Tig!) Night Blue Met (sold)
2006 Trailblazer SS Red Jewel Tint 395 HP AWD (sold)
2014 Silverado LTZ Crew 4WD
2012 Honda VFR 1200F Tahitian Blue (sold)
2015 BMW S1000R Racing Red
2013 Honda CBR500R Red (wife's bike)
2014 Triumph Bonneville T100
2003 Harley Davidson V Rod Anniversary Edition

Last edited by kenmosher; 11-08-2005 at 11:43 AM.
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