Let's revisit grounding a car

[leper84]

I don't know what yo mean by on off modules

The Engine Control Module will directly control and monitor switches and sensors using ground circuits wired directly into the ECM.

but the grounding in the car is simple enough.

Apparently not.

There's one ground from the engine to the chassis and everything rides off of that for the most part. I'm not hacking into anything and reworking the ground. Simply adding a few points

Sounds like you are. You stated you ran a new ground directly from your throttle body motor circuit.

I'm not going to spend the time looking up a wiring diagram specific to your car, but here is a general example.

The ECM will measure and supply voltage to the TB motor. The ground from the TB motor will return to the ECM where voltage will be measured again. Reason for this is in any direct current circuit a motor also acts as a resistor and the power consumption of the motor can be measured in the voltage drop.

What happened to your car may be one of two things, depending on the design of your car.

Maybe you tapped into a ground electrically similar at the TB and battery and its all placebo.

Maybe you tapped into a ground that is not electrically similar. Say you added a ground to a circuit going to the ECM, the two grounds would not be similar and your ground would be a brand new circuit. In that case, how could you know you aren't increasing current flow through the existing circuit by giving it an easier ground path than intended?

The ECM will measure a voltage drop across a circuit. If its the TB motor circuit, is the increased current causing the plate to stay open slightly more at idle?

If its the TB sensor circuit, it the increased current giving the ECM a flawed throttle position reading and causing it to either open the throttle more or send the car into a rich running safe mode?

In either case, a circuit controlled by the ECM is designed for a VERY specific range of voltage and current, and you risk burning up your ECM, TB and/or both. For example- early 2000's Nissan v6's would have IAC coils go bad. The resistance measured across the coil when good would be around 18 ohms IIRC. The resistance measured across bad coils would be 2ish ohms. That drop in resistance (what you're doing to your car) would be enough to burn out the ECM due to more current flowing through the circuit than it was designed for.


TL;DR: Grounds aren't just grounds in cars, you need to understand the circuit very damn well before you change anything.

 

[Pacfanweb]

How would you describe these old jeep ground points?

I agree that if I did ground a perfectly grounded car it would do nothing more than cause additional ground loops.

I am not convinced that this car I am working with have grounds out the wazoo. Either that or there was some serious ground corrosion.

So you don't know how many grounds the car has? Unless someone has disconnected them, there are certainly more than one.

Corrosion is a possibility....doubtful, but technically possible.

Resetting the ECM is the only thing you did that *might* have changed (temporarily) the way the car acted. The ground wire certainly did not.

 

[RLGL]

You need to invest in a multimeter if you're going to do electrical work like that.

Plus you should get some serious schooling in EFI theory and repair!!!

 

[Bryf50]

If there was such a simple cheap fix that would make a car better, there's no reason the manufacturer wouldn't have implemented it. Because it's in their best interest to make their cars as good as possible. The same goes for all the other cheap aftermarket shit that makes big claims.

 

[Lean L]

The Engine Control Module will directly control and monitor switches and sensors using ground circuits wired directly into the ECM.



Apparently not.



Sounds like you are. You stated you ran a new ground directly from your throttle body motor circuit.

I'm not going to spend the time looking up a wiring diagram specific to your car, but here is a general example.

The ECM will measure and supply voltage to the TB motor. The ground from the TB motor will return to the ECM where voltage will be measured again. Reason for this is in any direct current circuit a motor also acts as a resistor and the power consumption of the motor can be measured in the voltage drop.

What happened to your car may be one of two things, depending on the design of your car.

Maybe you tapped into a ground electrically similar at the TB and battery and its all placebo.

Maybe you tapped into a ground that is not electrically similar. Say you added a ground to a circuit going to the ECM, the two grounds would not be similar and your ground would be a brand new circuit. In that case, how could you know you aren't increasing current flow through the existing circuit by giving it an easier ground path than intended?

The ECM will measure a voltage drop across a circuit. If its the TB motor circuit, is the increased current causing the plate to stay open slightly more at idle?

If its the TB sensor circuit, it the increased current giving the ECM a flawed throttle position reading and causing it to either open the throttle more or send the car into a rich running safe mode?

In either case, a circuit controlled by the ECM is designed for a VERY specific range of voltage and current, and you risk burning up your ECM, TB and/or both. For example- early 2000's Nissan v6's would have IAC coils go bad. The resistance measured across the coil when good would be around 18 ohms IIRC. The resistance measured across bad coils would be 2ish ohms. That drop in resistance (what you're doing to your car) would be enough to burn out the ECM due to more current flowing through the circuit than it was designed for.


TL;DR: Grounds aren't just grounds in cars, you need to understand the circuit very damn well before you change anything.

I didn't tap into anything. It was more along the lines of Transmission chassis to battery and engine chassis to battery connections.

What about the throttle body motor? Does that ground to the TB instead of to the ECU? If there is less resistance for that circuit, it would actuate quicker possibly?

Again, just brainstorming here. Let me know if this has merit?

If there was such a simple cheap fix that would make a car better, there's no reason the manufacturer wouldn't have implemented it. Because it's in their best interest to make their cars as good as possible. The same goes for all the other cheap aftermarket shit that makes big claims.

I'd agree with you for a performance car. This family sedan may not have had so much thought put into it. Put it this way, I first drove a TSX and thought it handled great. Then I bought the accord and thought that the handling was okay but something was always off with its hesitation. The 8th gen v6 gets a lot of these comments. I might check the factory grounds when I get the chance to see they weren't rotted or something.