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Ive tested the harness all the way from the TCM sleeve connector (which btw leaks, but i cleaned it until i change it) up to the ECU plug and fuseboxes/ plugs and i found NO resistence at all. Cables are WELL. TCM and ECU i know both are ok.
Quick TCM cables description for those interested:
2 black grounds they bolt on the body by the wheel arch
2 pairs of green yellow canbus
2 signal wires orange & green red
1 Live positive - thick brown (from front fusebox)
1 ignition positive - green orange ( from primary fusebox)
Then i tested the positive cables voltage, compared to voltage measured at the battery(12.2v) and at random fuses from the front fusebox (12.2v):
- live positive = 12.2v (same as fuses)
- BUT the ignition positive was 11.7v. Therefore i tested the voltage back at its fuse (F15) in the primary fusebox (footwell) and it was still 11.7v. THIS CAN VERY WELL CAUSE P1643
Therefore I checked the electrical scheme, to see what powers F15. Feed comes from ignition, and also powers other 7 fuses in the same primary box. (Picture)
Since they are linked, i took those fuses out and did a parasitic test: i measured voltage to look for a draw, and i found one: FUSE 29 circuit was drawing 0.2v (the rest were all drawing ~ 0.04v). This is the difference missing from those 11.9v.
This F29 fuse drives power to the general electrical module, at ignition anti theft. (LH A pillar) - i will check it tomorrow,
And to other 3 modules that i dont have: parking, phone and voice. (Will check the trunk plugs for water)
#3 The last problem thats seems very imporant: While checking for parasitic voltage draws at the aforementioned ignition powered circuits, i also checked before the ignition, in the rear fuse box. (F3 powers the ignition).
I removed the fuse, and measured voltage at the pin that goes to the ignition: result was 10v draw, for 1 minute after i took the key out of the ignition. Is this normal?
Many thanks!
Last edited by elDariusVargas; Jan 1, 2022 at 10:15 AM.
I am attaching the same diagram below, but with some notes this time.
As seen, Cable WG powers some circuits through the primary fuse box when ignition is on (fuses in the diagram)
I did a test in order to help me understand what's causing low Voltage at the TCM in the circuit powered by F15..
(btw, Battery voltage =12.2v)
-First i set the ignition on and i measured the voltage between ground and the aforementioned fuses.=11.7v (very low);
-Then I pulled out F15 (powers: TCM, Jagate, generator);
-I measured the voltage between ground and point "B" (red): still 11.7v
-I step by step pulled out the other aforementioned fuses, and each time i measured the voltage between the same spots (ground and B): WHEN I PULLED OUT F4, voltage between ground and "B" measured 12v.
-I then PLACED BACK FUSE F4 and i measured the voltage between ground and point "A"(blue): IT MEASURED 1.5v!!
- I removed F4 again, and i measured voltage again between ground and B. This time was 0v.
why do i find a voltage measurement of 1.5v between ground and A, if the circuit coresponding to F15 is discontinued by having removed the F15 itself?
why is it behaving normal when i remove Fuse F4?
(I also removed te inertia switch to rule out some circuits and had the same results)
why do i find a voltage measurement of 1.5v between ground and A, if the circuit coresponding to F15 is discontinued by having removed the F15 itself?
I take it you're using a digital meter? I have about 8 different versions, and as much as I like 'em, they can give misleading results at times. Digital meters draw so little current, they can show voltage available when it's not really a valid measurement. You could call it ghost voltage or something like that, as it's not anything usable. It can really trip you up while troubleshooting. I do not care to discuss how I learned this, especially how many times I fell for it.
Even with that circuit isolated by removing the fuse, your meter could be picking up something like a capacitor draining down inside some module. Once again, nothing usable. The voltage goes way when you reinstall the fuse because the teensy voltage present finds another path to ground through another circuit parallel with that fuse.
If still not convinced, here's a practical example. Switch your meter to AC volts, but don't connect it to anything. Hold your meter and leads up to a fluorescent light. Many digital meters will show several volts of this meaningless ghost voltage. Not quite the same thing measuring AC, but it should give you an idea of how overly sensitive a digital meter can be.
I take it you're using a digital meter? I have about 8 different versions, and as much as I like 'em, they can give misleading results at times. Digital meters draw so little current, they can show voltage available when it's not really a valid measurement. You could call it ghost voltage or something like that, as it's not anything usable. It can really trip you up while troubleshooting. I do not care to discuss how I learned this, especially how many times I fell for it.
Even with that circuit isolated by removing the fuse, your meter could be picking up something like a capacitor draining down inside some module. Once again, nothing usable. The voltage goes way when you reinstall the fuse because the teensy voltage present finds another path to ground through another circuit parallel with that fuse.
If still not convinced, here's a practical example. Switch your meter to AC volts, but don't connect it to anything. Hold your meter and leads up to a fluorescent light. Many digital meters will show several volts of this meaningless ghost voltage. Not quite the same thing measuring AC, but it should give you an idea of how overly sensitive a digital meter can be.
many many thanks!!
may i ask about one issue that i am still trying to figure out;
if i measure the voltage, in the primary fusebox, at Fuse15 (or F29 for instance) it reads 11.7v.
Car is off and battery reads 12.2v, same do the fuses in the front fusebox: 12.2v.
Is it normal to have a slight lower voltage in the primary fusebox?
Is it normal to have a slight lower voltage in the primary fusebox?
Yes and no. How's that for a definitive answer?
The big issue I'm seeing here is how voltage readings behave in an unloaded circuit. I touched on it previously, that you can get misleading results and head off down the wrong path.
Here's a good rule of thumb: Voltage readings don't always mean anything in an unloaded circuit.
On an unloaded circuit, if you see normal voltage at a particular point, that's a step in the right direction. But it's not conclusively a good thing, and the apparently good reading can mask a problem where the voltage drops off under load.
Think of a basic unloaded voltage check as only a very preliminary step. If it fails, you know to look for a bad switch or broken wire, so it's an important step. If it passes, it confirms the circuit is more or less intact, any switches have activated, etc. So this is still good, just not conclusive. For that, you want to check voltage while loaded (the circuit, not you). This is the important follow-up step that often gets overlooked. Most people aren't even aware of this, as an unloaded voltage check finds the problem in most cases. Those are the cases where my boss calls me on my day off to help get a plane over the fence and out of town.
So back to the minor difference in voltage you recorded. Probably not a problem. Could be when you set up to take a reading at the primary junction box, other circuits get powered too. This drops the available voltage slightly.
For investigating a suspect wire, don't forget to check for any continuity to ground, such as a bare spot rubbing against the chassis. The wire will still check fine for continuity end to end, but the circuit falls down under load. If you're lucky, this unwanted path draws enough current to blow a fuse, and then the fault is fairly easy to diagnose and locate. But if only making light contact? That can be enough to skew a sensor input, but not enough to be super obvious. I had one of those the other day on a 737 antiskid. Took about 2 hours of methodical testing before we found it.
If you suspect a certain wire, it may be easier to temporarily run a new wire for testing. Totally disconnect both ends of the existing wire so you don't inadvertently retain a short to ground, for example.
The big issue I'm seeing here is how voltage readings behave in an unloaded circuit. I touched on it previously, that you can get misleading results and head off down the wrong path.
Here's a good rule of thumb: Voltage readings don't always mean anything in an unloaded circuit.
On an unloaded circuit, if you see normal voltage at a particular point, that's a step in the right direction. But it's not conclusively a good thing, and the apparently good reading can mask a problem where the voltage drops off under load.
Think of a basic unloaded voltage check as only a very preliminary step. If it fails, you know to look for a bad switch or broken wire, so it's an important step. If it passes, it confirms the circuit is more or less intact, any switches have activated, etc. So this is still good, just not conclusive. For that, you want to check voltage while loaded (the circuit, not you). This is the important follow-up step that often gets overlooked. Most people aren't even aware of this, as an unloaded voltage check finds the problem in most cases. Those are the cases where my boss calls me on my day off to help get a plane over the fence and out of town.
So back to the minor difference in voltage you recorded. Probably not a problem. Could be when you set up to take a reading at the primary junction box, other circuits get powered too. This drops the available voltage slightly.
For investigating a suspect wire, don't forget to check for any continuity to ground, such as a bare spot rubbing against the chassis. The wire will still check fine for continuity end to end, but the circuit falls down under load. If you're lucky, this unwanted path draws enough current to blow a fuse, and then the fault is fairly easy to diagnose and locate. But if only making light contact? That can be enough to skew a sensor input, but not enough to be super obvious. I had one of those the other day on a 737 antiskid. Took about 2 hours of methodical testing before we found it.
If you suspect a certain wire, it may be easier to temporarily run a new wire for testing. Totally disconnect both ends of the existing wire so you don't inadvertently retain a short to ground, for example.
Hope these vague ramblings help.
perfect thank you! Im now finished charging my battery since that low voltage can be a big source of problmes.
I forgot to mention one more thing. When checking a harness, look for continuity between the suspect wire and others in the bundle. With both ends disconnected, there should be no continuity, or infinite resistance.
Wiggle the harness when testing, too. This helps find any intermittent faults.
I forgot to mention one more thing. When checking a harness, look for continuity between the suspect wire and others in the bundle. With both ends disconnected, there should be no continuity, or infinite resistance.
Wiggle the harness when testing, too. This helps find any intermittent faults.
MANY THANKS for all the help!
now everyone, i've concluded my case.
Firstly ive tested all the TCM To ECU cables and were fine, because the cowl and the plugs were already disassembled, and was handy to do so.
But,
As i said the TCM connector was leaking oil. My appointment at the elevator came up yesterday, si i've changed the sleeve itself, cleaned the connectors of tranny oil, using brake cleaner, compressed air and then connection spray.
Solved the issue. Transmission shifts like new.
no metallic dust on the magnets inside the oil pan so im very happy
Glad to hear it's fixed. Yes we have had many cars with the leaking sealing sleeve also having TCM problems. Appears the transmission fluid works it's way back into the harness/wires over time causing problems. Never the same problems but usually involving the TCM or CAN bus errors.
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Update: S Type Electrical Issues and P1643 testing. Please help!
