Skip the auto shop - Our mechanics make house calls

Q: Please help me diagnose an electrical drive by wiring

asked by on

I performed pin by pin test on wiring according to manufacturers service manual, I have two seemingly ambiguous results, the first is 50.7 ohms of resistance in the F terminal of the APP wiring terminal and the main relay terminal A. I attributed this to the evap leak detection pump which shares this wire since that is at the top end of normal resistance between power and ground (terminals A & B) for that component. Is this correct? Secondly in the manufacturers (mazda) manual it refers to continuity between the ground terminal and the power supply of both the APP and the Evap leak detection pump as a short circuit. Isn't that a complete circuit and totally normal?
My car has an automatic transmission.

Hello. Generally speaking, most automotive circuits have very low resistance, usually less than 50 ohms. Unless there is a resistor, or sensor that acts as a resistor between the APP wiring terminal and main relay terminal A, then there may be some sort of wiring issue causing the excessive resistance. I would refer to a service manual or dealership for specifics on what the readings should be for the circuits in question. If the manual indicates that there should be no continuity between those circuits, then that may indicate that those circuits have grounds that are switched on an off, usually by the computer. If you are getting readings outside of normal range then it may be possible that there is an issue with your test leads, or a wiring issue with the circuits in question. Contact a professional mechanic, such as one from YourMechanic, if you want to have a technician inspect your circuits for you.

Was this answer helpful?

Need advice from certified mechanic? Get help now!

Over 1000 mechanics are ready to answer your question.
The statements expressed above are only for informational purposes and should be independently verified. Please see our terms of service for more details

Get an instant quote for your car

Our certified mechanics come to you ・Backed by 12-month, 12,000-mile guarantee・Fair and transparent pricing

Get a quote

What others are asking

Q: Engine Light and AT light. Car goes into limp mode

Hello. Most of the time this is the result of a transmission failure. It is common for this transmission to have internal pressure problem which will cause these codes. It can also be a voltage problem so I always check...

Q: Major oil leak

Hi. Large oil leaks can be difficult to pinpoint because they get all over the undercarriage. The best way to find a leak is to clean off the engine and then add dye to the system. Running the engine with...

Q: Steering wheel is hard to turn but turns back straight easily

Hi there: It's possible that you're power steering pump might be faulty or perhaps damage to steering components such as tie rods, or steering column. Due to the fact that there are multiple mechanical components that might be causing the...

Related articles

How Do Power Car Windows Increase Passenger Safety?
Power windows are responsible for approximately 2,000 emergency room visits every year. When a power window closes, it exerts enough force to bruise or break bones, crush fingers, or restrict an airway. Though...
How Long Does a Heater Control Valve Last?
Keeping the right amount of coolant in a car is essential in keeping the engine at the right temperature. Failing to have the right amount of coolant or even bad elements...
What are the Car Pool Rules in Hawaii?
Hawaii is widely regarded as a land of vacation and relaxation, and as such, its scenic roads and routes are far better known than the state’s freeways. But, as with all...