Milliamp Current Testing

Darren Mechanic West Allis, Wisconsin Posted   Latest  
Question
Driveability
2002 Lexus ES300 3.0L (1MZ-FE) 5-spd (U150E)

suspect bad connection somewhere in circuit so I thought to check circuit integrity with milliamp clamp 10 mv per milliamp. this is a cam sensor signal wire, the voltage signal is identical but inverted, any thoughts? 3 wire sensor. 

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Darren Mechanic
West Allis, Wisconsin
Darren Update
 

P1350 code, intermittent. No codes at time of testing.

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Caleb Technician
Mishawaka, Indiana
Caleb Default
 

I'm not sure exactly what your asking. But amperage will usually look the opposite of voltage. If you want to change how it looks on the screen flip the amp clamp 180 degrees or hit invert on the scope setting. Dont overthink it, the car isnt broke right now.

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Darren Mechanic
West Allis, Wisconsin
Darren Default
 

Just wondering if it’s a good approach to lets say a intermittent connection issue....

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Caleb Technician
Mishawaka, Indiana
Caleb Default
 

Yes its a very good approach . I just dont have a microamp clamp yet so I havent had a chance to try it. The idea is if you have an open the microamps will go low. If you have a short to ground the microamps will go high.

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Geoff Diagnostician
Lahaina, Hawaii
Geoff Default
 

No, load testing the wires is a good approach. Milliamps can still travel through poor connections just fine. Check pin fit (drag test), wiggle test, replace sensor.

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John Technician
Auburn, California
John Default
 

A cam sensor does not draw current. If I suspect a bad connection, I ground the wire at the sensor and load test it with a taillight bulb at the ECU. Unplugged of course... lol.

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Caleb Technician
Mishawaka, Indiana
Caleb Default
 

Hey John you are correct that the cam sensor doesnt not draw a lot of current. However you will notice Darren is talking about a MICROamp clamp. When the sensor switches from 0-5v or vice versa there is definitely a change in amperage no matter how small. Think about the newer Chrysler Hall effect ABS sensors. Chrysler actually states in description and operation that the ABS module will only…

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Matthew Mobile Technician
Bartlett, Illinois
Matthew Default
 

With a Lexus you will not see electronics in the wiring diagram, but the circuit diagram in the diagnostic section will show you electronics. There are two types of sensor signals. Some sensors get 5 volts and pull it to ground, some create voltage. See the two diagrams I drew attached. I would be less worried about the current for a cam signal. My approach is testing the signal at the ECM and…

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Caleb Technician
Mishawaka, Indiana
Caleb Default
 

Okay so clearly I am not making myself clear. I'm not saying Darrens method is the only way to test it,but simply a way of testing. I think instead of me trying to further explain myself ill post this link to a DiagNet case study which beautifully explains what I am trying to say diag​.​net/msg/m6i0er9wig…

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Diogo Owner/Technician
Fortaleza, Brazil
Diogo Default
 

Acredito que um bom ohmímetro ainda é a melhor ferramenta para estes casos.

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