Hall Sensor








The following testing procedures apply to distributor mounted TFI modules, and are a follow-up procedure of the How to Solve an EFI No Start thread at www.SBFTECH.COM. In order to proceed, you will need a few tools and equipment.



*      Digital Volt-Ohm meter (VOM)

*      TFI module socket wrench

*      TFI system Wiring Diagrams



Where is the TFI mounted?  It’s mounted on front of the distributor and plugs into the EFI harness from the computer and connected to the Hall Sensor on the distributor end.  The Hall Sensor is mounted inside the distributor and it’s bound by the distributor shaft and octane sensor.  The Hall sensor connector is also mounted in the distributor and is responsible for transmitting magnetic pulses to the TFI module indicating crank location.







    TFI Module Attached to Distributor Stator Sensor/TFI Module Connector Pinout          


What are the expected test ranges for TFI modules? Well, first lets reference the pins as A, B, C, and 1,2,3,4,5,6.  REMOVE the TFI module, and then we can measure resistances.  If you attempt to measure resistances otherwise, you will get interference from the Hall Sensor. 






A = Ground
B = PIP Power, Profile Ignition Pickup Power.  Powers the Hall Sensor in conjunction with terminal A .
C = PIP IN, Ignition signal picked up via the Hall sensor sent to the TFI module.
1 = PIP, Profile Ignition Pickup.  PIP signals the EEC of the crankshaft position.
2 = SPOUT, Spark Output Signal from the EEC module.  This is how EEC controls your timing.
3 = START, Battery voltage input with ignition switch in start position.
4 = TFI PWR, Battery voltage input with ignition switch in run position.
5 = TACH (IDM), Tachometer, Ignition Diagnostic Monitor, Switched output to ignition coil.
6 = IGN GND, Ground.

The following is a comparison made between two modules, one with 100k miles and a relatively brand new module (A2A).

PINS    EXPECTED VALUES            A1A(100kmiles usage)     A2A (10miles usage) % diff
NOTE: 14.26kohms = 14,260ohms

A to C   > 500ohms                             14.26kohm              14.15kohm            -0.77%
B to C   < 2,000ohms                           1.112kohm             1.115kohm           +0.27%
B to 4   < 200ohms                              84.7ohm                86.1ohm               +1.65%
A to 6   < 2ohms                                  0.0ohm                  0.0ohm                  0.0%
C to 1   < 200ohms                              101.2ohm               100.8ohm              -0.40%


Here is another set of tests to complement the above, measurements are in OHMS:













D1 to H1


D2 to H1


D3 to H1


D1 to D2 


D1 to H2


D2 to H2


D3 to H2


D1 to D3


D1 to H3


D2 to H3


D3 to H3



D1 to H4


D2 to H4


D3 to H4



D1 to H5


D2 to H5


D3 to H5



D1 to H6


D2 to H6


D3 to H6





1.  You must determine if a PIP signal is evident.  This can be accomplished by checking the voltage from the PIP signal.  It should be from 3 to 6v if using a volt meter. Or you can use a test bulb and should see it blinking.

2. The connector should be plugged up and then you should connect the positive lead of the volt meter to the #1 pin (the top one) on the connector. You will have to either use a splice connector or remove a small area of the insulation on the wire. Then connect the ground to any ground. Oh, the top wire is dark blue in color.









3. Start the engine and watch the voltage. It should be 3 to 6v or a blinking light or LED if you choose to test via that method.  The bulb/LED blinking method is easier.  The use of a digital volt meter will help identify that the voltage is steady on crank up, drops in the digital readout would identify the voltage as pulsating.







4.    If all else fails, remove it and replace it. If you check the new sending unit, it should have 0 ohms. A bad unit will show around 15,000ohms between points A and C.


5.    The following typical TFI diagram will also help understanding how the system works.

















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