ECU / wiring loom testing ?

[bembo449]

im seeking advice on testing the wiring harness to my ECU , do i use a multi meter , or is there a better method ??
thanks

 

[Botus]

is this on a 221 ? the cam sensors weep oil down the loom to the engine - and the gunk (acids, moisture, other combustion filth) blows up the ECU - happens a lot - USA had recall for 4 gunk stoppers that reduce likelihood

unless you can connect to a pin with a connector like the original loom and then use crocodile clip to the meter, you can't make sense of any numbers - some interesting youtube videos of nerds fixing bosch ones on BMWs

 

[bembo449]

no pal its on my maserati ghibli diesel , its only firing on one bank , theres no pulse to the other bank of injectors and the ECU is new and dealer fitted / coded so it really only leaves wiring harness at fault i think

 

[M80]

Assuming the connectors are small, like MB's, be careful not to splay open those by inserting meter probes. I had a V6 CDI with bad connections at sensors due to this. Testing from the ECU end I could get unreliable readings of the sensor by wiggling at the sensor.

My method now is to croc connect to needles and insert the needles into the connectors.

 

[bembo449]

duly noted M80

 

[mattkh]

My method now is to croc connect to needles and insert the needles into the connectors.

How about a tiny bit of copper grease on the tip of the probe when touching the connector pin jaw..???

 

[M80]

How about a tiny bit of copper grease on the tip of the probe when touching the connector pin jaw..???

Useful as it is I wouldn't want that stuff floating about near these multi connectors.
If it got into the congested areas who know's what readings might result.

 

[supernoodle]

I use these things, nice positive 4mm jack rather than having to use croc clips.

Pardon our interruption...

www.ebay.co.uk

A multimeter is useful to check the point to point wiring integrity. Not great for determining if a signal is any good though.

To check injector signals you really need a scope and current clamp. Check out mechanic mindset on YouTube. He shows a cheap(ish) solution, picoscope and clamp. The scope is very useful for lots of other tests too, so a good investment of you're doing lots of electrical work.

I have known an ECU not to throw an error if an injector was open circuit, so to have a bank down and no error is odd.

 

[M80]

I use these things, nice positive 4mm jack rather than having to use croc clips.

Pardon our interruption...

www.ebay.co.uk

A multimeter is useful to check the point to point wiring integrity. Not great for determining if a signal is any good though.

To check injector signals you really need a scope and current clamp. Check out mechanic mindset on YouTube. He shows a cheap(ish) solution, picoscope and clamp. The scope is very useful for lots of other tests too, so a good investment of you're doing lots of electrical work.

I have known an ECU not to throw an error if an injector was open circuit, so to have a bank down and no error is odd.

Far better than my botch.
Very similar I've ordered these.
For me red / black is better, but when testing many points I can see the 5 colours having advantage.

Pardon our interruption...

www.ebay.co.uk

 

[supernoodle]

I have known an ECU not to throw an error if an injector was open circuit, so to have a bank down and no error is odd.

Oops this should have read "never known an ECU not to throw an error".

Piercing probes can be useful too if you can't get to a connector. I've got the Fluke versions of these, but if you're not using them much these copies might be worth a go.

Pardon our interruption...

www.ebay.co.uk

 

[ajlsl600]

Might add them to my t box. I always hate it when I see wires pierced right next to the plug. I prefer to be 10 inches away, easier to avoid damage to insulation right next to plugs, adaptors

 

[bembo449]

I use these things, nice positive 4mm jack rather than having to use croc clips.

Pardon our interruption...

www.ebay.co.uk

A multimeter is useful to check the point to point wiring integrity. Not great for determining if a signal is any good though.

To check injector signals you really need a scope and current clamp. Check out mechanic mindset on YouTube. He shows a cheap(ish) solution, picoscope and clamp. The scope is very useful for lots of other tests too, so a good investment of you're doing lots of electrical work.

I have known an ECU not to throw an error if an injector was open circuit, so to have a bank down and no error is odd.

i do have a clamp meter , ive never known a car not to throw a code for injector issues , its very odd

 

[ajlsl600]

Unless canbus compromised?? But that should come up on diagnostics!!

 

[bembo449]

there is a code for canbus as it happens

 

[supernoodle]

Injector control doesn't care for anything CAN.

As you have one bank working I expect if you disconnect one of the working injectors you'd get a open circuit error. That will tell you that they at least calibrated them.

A current clamp and clamp meter aren't the same. Clamp meters are usually only for AC current and just a display. You need something that measures DC current and has an output, like this

20 A / 60 A DC (low amps) current clamp

Low current clamp for measuring Injectors, sensors and actuators around the engine. An invaluable part of any scope diagnostic kit

www.picoauto.com

 

[M80]

I have an AC / DC clamp meter.
Using it for DC I would be cautious about trusting the accuracy, but really that can be similar with AC clamp meters. Moving them around on a cable can vary the field strength and so the readout. And with DC clamps there is a degree of polarity conscious.
More often though we just want to see evidence that there is a current drawn. Open cct, or lack of a supply means it 'aint doing anything.

 

[bembo449]

i decided to invest in an oscilloscope , just seemed a good idea if i need to test all the harness

 

[supernoodle]

Picoscope? Or standalone?

 

[mioba]

How about a tiny bit of copper grease on the tip of the probe when touching the connector pin jaw..???

silly idea tbf, spreads like **** and sure short. Not what its made for