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Amp clamp key-on erratic graph

  • radau
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07 Nov 2019 05:17 #34809 by radau
Amp clamp key-on erratic graph was created by radau
Hi all,

Was doing some testing and noticed that when using an amp clamp on my battery cables (negative or positive) I get a very erratic graph. I checked another car and I get a nice flat line with it just sitting there key on engine off.

Key off I get a nice solid line on the Hyundai, it's only when the key is switched on that I see this.

Anyone know what could cause this? Vehicle is a 2007 Hyundai Santa Fe.

Image in case attached doesn't work i.imgur.com/8NzDlDZ.jpg

Thanks!
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07 Nov 2019 05:42 #34810 by Cheryl
Replied by Cheryl on topic Amp clamp key-on erratic graph
Weird. Guess you could try pulling fuses until it goes away then see what the fuse feeds if you really wanted to. If it’s not killing the battery and it was my car I wouldn’t worry about it

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07 Nov 2019 11:43 #34822 by radau
Replied by radau on topic Amp clamp key-on erratic graph
With the key off I don't get the drop outs like there is here, only with the key on it looks like this.

Only issue I'm having is that my secondary K-Line voltages get dropped on the OBD2 connector whenever the PCM is connected and it appears to be whenever the relay control wires get connected to the PCM.

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07 Nov 2019 17:05 - 07 Nov 2019 17:05 #34830 by radau
Replied by radau on topic Amp clamp key-on erratic graph
Checked the ignition switch power distribution and it says that it feeds the following only when the key is "ON", issue was not present on ACC or off:

Feed #1:
Cluster (10A), ATM Lock (10A), T/SIG (10A), A/BAG IND (10A), BCM #1 (10A), A/BAG #1 (15A), A/BAG #2 (15A

Feed #2:
BCM #2 (10A), AC Inverter 2 (10A), RR Wiper (15A)

Disconnecting the Cluster fuses makes it go away entirely. Any ideas for where to go from here? Would a bulb be able to cause this?

Thanks!
Last edit: 07 Nov 2019 17:05 by radau.

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08 Nov 2019 13:45 #34850 by radau
Replied by radau on topic Amp clamp key-on erratic graph
Finally found the diagram in Mitchell for that, looks like more than just the cluster on that circuit, diagram attached and cluster fuse is at the bottom left corner.

This is causing voltage drop (from 13.5 to 10V) and a lot of noise on my PCM signal lines and it goes away entirely with the Cluster fuse out. PCM still can't communicate but wonder if it ended up getting damaged from this.
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08 Nov 2019 15:18 #34853 by TheTechWhisperer
Replied by TheTechWhisperer on topic Amp clamp key-on erratic graph
Put the cluster fuse back in and unplug the alternator, then re-check.

"You will always find the greatest fulfillment in life when you are operating in the gifts God gave you"- Dad

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08 Nov 2019 17:02 #34856 by radau
Replied by radau on topic Amp clamp key-on erratic graph
Not able to reach down there to fully disconnect it but I unplugged the small connector going to it with no change.

Leaving the Cluster fuse out to stabilize the amps, if I actuate any of my trans solenoids I get a rapid buzzing sound and the following amperage i.imgur.com/uayaIHb.jpg

These circuits are unrelated but giving similar results, any ideas? I have two PCMs and both do the same

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09 Nov 2019 15:56 #34878 by radau
Replied by radau on topic Amp clamp key-on erratic graph
Was referencing AllData and found out that I disconnected the PCM connector, not the Generator plug which is on the back-side of the alternator next to the main cable.

Did not realize that the PCM had a wire running to this until I viewed the "charging system" diagram (attached) which gives me a common point between 2 odd readings.

Not at home so wont be able to check the car for a few days but going to disconnect that fully and see if commanding solenoids on still provides an erratic amperage or if it smooths out.

Thanks all!
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12 Nov 2019 00:48 - 12 Nov 2019 00:49 #34943 by radau
Replied by radau on topic Amp clamp key-on erratic graph
Hi Tech Whisperer,

I put the fuse back in and disconnected the 3 pin connector on the back of the alternator that was labelled as "Generator" in the diagram and the erratic draw mostly went away

I can not communicate with the PCM at all via OBD2 with this disconnected, any idea if this is standard behavior due to a missing communication line from the PCM?

There is still some slight spiking when the key is first turned on that comes and goes then eventually goes away entirely. Photo attached of one of those events.

Does this confirm that the alternator should be replaced or do you know of any other checks I should run?

Thanks!
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Last edit: 12 Nov 2019 00:49 by radau.

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12 Nov 2019 01:00 #34944 by radau
Replied by radau on topic Amp clamp key-on erratic graph
Attached a photo of the key-on with the cluster fuse removed. There is no noise after the event whereas with the fuse in you will get some noise every few seconds until about 20 seconds in then it goes to a flat graph.

Cluster itself is currently disconnected which leaves the BCM and semi-active engine mounting module in that circuit. BCM was disconnected with no effect on amp draw but have not removed the panels to get to the semi-active engine mounting module yet.

Is the noise with the cluster fuse connected that goes away after about 20 seconds normal or should I continue investigating on that circuit then retry connecting the alternator if I find the cause? Or does this look like a bad alternator?
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12 Nov 2019 02:58 #34946 by radau
Replied by radau on topic Amp clamp key-on erratic graph
Got the scanner to reconnect finally after about 20 minutes of trying, actuating a solenoid still results in any solenoid buzzing and the erratic amps coming back on the ground clamp.

I've been trying to clamp my ammeter on some fuses with a fuse buddy but having to restart the ignition for certain fuses means that I'm back to the 20 minutes of getting the scanner to reconnect to even attempt to check it.

Seems like the alternator may not be at fault here but possibly something else common between the two circuits?

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13 Nov 2019 10:32 #34979 by TheTechWhisperer
Replied by TheTechWhisperer on topic Amp clamp key-on erratic graph
Sorry for the delayed response. I don't contribute on this forum very often, because my job requires me to travel all over the country to train Technicians almost every week, so it's really spotty when I have availability to jump on here. Unfortunately, I think people might assume I am "ghosting" them, but it's just my schedule, haha.

I have a few questions and also a few statements about this case of yours:

-Are you suspecting that this is causing a problem with the vehicle, or is there a symptom you are trying to diagnose?

- If the answer to the above question is "No", then is this just an observation you made while fiddling with the car? If so, I assume you just are curious "Why does my car do this and another car doesn't?" (if so, I can relate)

- I know that you are probably wondering why I asked you to unplug the alternator, and I will fully explain why. I can also explain the pattern that you are seeing right now. But first, I want to understand if you want help fixing an actual problem with the car, or if you are just trying to understand what you are seeing. Because if you need help fixing a legit problem or symptom, I want to cut to the chase and help you fix that first. Then if you want to understand the signals, I will explain it if you'd like.

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13 Nov 2019 11:16 - 13 Nov 2019 11:27 #34980 by radau
Replied by radau on topic Amp clamp key-on erratic graph
No worries on the delay

The issue I started off with was an intermittent P0741 which was able to be read with an Actron scanner. When I attempted to hook up the SnapOn Modis to do a bidirectional control test I got no com and when using Hi-Scan sometimes it communicates immediately but cannot read codes it just allows me to do bidirectional controls but sometimes gets disconnected as well.

With the SnapOn OBD2 cable connected and the PCM disconnected, my 3 K-Lines read 11V key on (6V key off), once the PCM is connected (just the right side connector "C-30A" needed to reproduce) only one of them reads 11V and the other 2 read 4.5V key on and 3V key off.

Since I couldn't use the scanner I hooked up my test leads and drove the car and got a similar graph for the TCC solenoid engaging, where instead of a steady signal it was very jagged. When actuating any of the shift solenoids with Hi-Scan they make a loud buzzing sound instead of a click. If ground is supplied directly to them from the PCM harness you will hear a solid click, so somewhere from the PCM back is causing this rapid cutting in and out. Duty Cycle reading was 50% as it averaged between 100% and 0%.

I unplugged the trans connector again and used my power probe in driver test mode and I don't see that erratic amperage anymore but the PCM doesn't fully ground the device, test light is the same as you can see it rapidly flickering rather than a solid light and get the same erratic volts graph on the ground wire but not erratic current so I'm thinking that's just from the solenoid cycling on and off really fast.

It seems like something is causing the PCM to cut in and out a bit but having a hard time figuring out what it could be. Possibly an overloaded ground? Bad sensor? Haven't seen this sort of symptom anywhere else in my searching and just unsure of what could be bringing it down. Have tried unplugging pretty much every module and CAN communication seems ok regardless.

Engine solenoids control fine from Hi-Scan, it's just the transmission solenoids that buzz and the 2.7L Santa Fe only has a single PCM to control both the engine and trans it looks like.

Thanks!
Last edit: 13 Nov 2019 11:27 by radau.

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13 Nov 2019 16:44 #34988 by radau
Replied by radau on topic Amp clamp key-on erratic graph
Went ahead and got a quick video using a brand new solenoid, eliminating the 12V supply from the equation here so it's just PCM/ground so you can hear the noise that ends up being associated with the waveform.

Jumper wire pins are smaller than the connector end but still have good contact how I have them resting.

Similar result in driver test mode on the power probe, you will see the voltage dip like it's trying to ground but the constant on/off prevents it from reading a solid ground.

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13 Nov 2019 17:24 #34989 by radau
Replied by radau on topic Amp clamp key-on erratic graph
Here's another video, same set-up as the previous but have the Modis on the alligator clip at the ground control wire and battery negative to graph the voltage.

Do you know if the slight voltage reading with the power probe connected without supplying any voltage/ground is to be expected on a driver circuit or is this indicating a fault in the PCM as there shouldn't be ground? With the PCM disconnected I get no reading on the power probe display and if I move my solenoid ground to battery negative I get a solid 0V reading without fluctuation.

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18 Nov 2019 19:56 #35122 by radau
Replied by radau on topic Amp clamp key-on erratic graph
Bit of a bump.

Picked up a Delphi DS150e scanner which appears to retry if a connection fails so have a more consistent way of getting a scan tool going even though it's still intermittent on the first connect. Put the car back together for now and still has the solenoids buzzing.

Checked ohms to ground on the ATM relay (pin 87) which powers the solenoids and oil sensor, as well as provides power feed on pin 60 of the PCM C30B connector. With everything connected up I get 400 ohms to ground, if I use the power probe it will periodically flash green telling me that it is grounding intermittently on that circuit.

This measurement was taken both with key off and key on with no change.

Going to pull the air box back out tomorrow and get the connector removed and do some more measurements.

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21 Nov 2019 02:29 #35177 by radau
Replied by radau on topic Amp clamp key-on erratic graph
Did some fuse box testing without the battery tender on and guess I just didn't realize the voltage drop before.

Nearly all of my key on circuits have a voltage drop so I worked my way through the circuit back to the ignition lock cylinder. The power feeds read battery voltage, but the power output measures a 0.37V drop. My power probe in feed test mode reads 10-12 ohms with the loaded circuit test for what it's worth.

I used a set of LoadPro leads I had on my multimeter it brings the voltage down even further (roughly another 0.5V drop). Could this possibly be affecting my PCM? The car does have ~140k miles on it and the lock cylinder has never been replaced so I'd imagine the contacts are somewhat worn down.

Tried to disconnect the connector from the lock cylinder but these old connectors on the car sure do get really stuck so called it a night there.

Any insight is appreciated, thanks all!

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