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Air Flow Meter – Hot Wire

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 Author| Post time 2019-3-5 08:25:41 | Show all posts
Note: the switch will have three wires normally consisting of:
(i) idle circuit contacts
(ii) full load circuit contacts
(iii) earth
Check the technical data for the system to be tested.


Figure 6.3.1


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 Author| Post time 2019-3-6 08:49:54 | Show all posts
Operation Steps

1. Open the software, select “Vehicle->Diagnosis->Setup”, as illustrated in Figure 6.3.2.


Figure 6.3.2


2. Click “Sensors->Throttle Position -> Throttle Position Switch”, and click “OK”, as illustrated in Figure 6.3.3.




Figure 6.3.3


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 Author| Post time 2019-3-7 08:14:32 | Show all posts
Reference waveform


Figure 6.3.4
Example waveform


Figure 6.3.5 Idling 850


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 Author| Post time 2019-3-8 09:24:38 | Show all posts
Notes:

The Throttle Switch (TS) is invariable a three wire device operating at 5 volts (12 volts on very early systems).
The objective of the throttle switch is to inform the Electronic Control Module (ECM) of the position of the throttle
movement at throttle housing.

The example waveform shows a dual trace picture, monitoring the two switched terminals of the TS. The throttle
has been operated from rest to full throttle and back to rest. The yellow trace is the idle contact circuit, once the
throttle starts operating this switch opens and its voltage changes from 0 to 5 volts. It will remain at 5 volts, even
at full throttle, until the throttle is back at its idle position.

The blue trace is the full load circuit and is at 5 volts (in its open position) until full throttle is achieved. As the operator
only stayed in the full throttle position for a very short period (560 ms) the switch soon opens again and the voltage
changes back from 0 to 5.

This device can be switched in several ways, so it will be necessary to check with the vehicle and module specific data.
Inside the switch there are two sets of contacts, this enables three stages of throttle movement to be monitored.
These are:
u Throttle closed
u Throttle part open
u Throttle fully open (sometimes referred to as wide open throttle - WOT )


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 Author| Post time 2019-3-11 08:30:15 | Show all posts
Injectors Single Point (Voltage)
Single Point Injector (SPI) is also sometimes referred to as Throttle Body Injection (TBI).
A single injector is used (on larger engines two injectors can be used) in what may have the outward
appearance to be a carburettor housing.

The resultant waveform from the SPI system will show an initial injection period followed by multi-pulsing
of the injector in the remainder of the trace. This section of the waveform is called the supplementary
duration and is the only part of the injection trace to expand.


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 Author| Post time 2019-3-12 08:12:26 | Show all posts
Connect the oscilloscope
1. Plug the 20:1 Attenuator into channel 1 on the DSO3064(A) and the BNC test lead (HT30A) into the
other end of the attenuator. Place a large black gator clip(HT18A) on the test lead with the black moulding
(negative) and an acupuncture(HT307) or multimeter probe onto the test lead with the red moulding (positive).

2. Attach the black gator clip onto the battery negative terminal and probe the switched earth side of the
injector with the acupuncture or multimeter probe as illustrated in figure 6.4.1.


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 Author| Post time 2019-3-13 11:39:06 | Show all posts
With the example waveform displayed on the screen you can now hit the space bar to start looking at
live readings. Snap the accelerator quickly from idle to full throttle and observe the supplementary injection
of the waveform expanding under acceleration.


Figure 6.4.1


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 Author| Post time 2019-3-14 09:10:44 | Show all posts
Operation Steps:

1. Open the software, select “Vehicle->Diagnosis->Setup”, as illustrated in Figure 6.1.2.
2. Click “Sensors->Injector Diagnonis -> Single-point Injector(Voltage)”, and click “OK”, as illustrated in Figure 6.1.3.



Figure 6.4.2


Figure 6.4.3


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 Author| Post time 2019-3-15 08:08:33 | Show all posts
Reference Waveform

Figure 6.4.4


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 Author| Post time 2019-3-16 08:13:25 | Show all posts
Example Waveform


Figure 6.4.5


Notes:
Neither wire of the injector should be connected to the negative (ground) input of the oscilloscope as this could
cause a short circuit.
The 20:1 Attenuator is used to monitor the induced voltage that is created when the earth path to the injector is
removed. This voltage will be in the region of 60 to 80 volts.


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