SaabCentral Forums banner

1 - 20 of 25 Posts

·
Registered
Joined
·
10 Posts
Discussion Starter #1
I recently Bought a 04 ARC 9-3 Had a litany of codes but for 2500$ it seemed like a solid car, previous owner drove it with codes for 6+months no problems other than previously mentioned white smoke, low boost ETC.
Anyway i sent the ECU to a company to have the boost chip and fuel injector chip replaced.
during this they requested I also replace Injectors with oem rebuilt, new spark plugs, new boost and vacuum solenoids.
Got the ecu back and it worked amazing for 2 weeks. then all the codes and issues came back sent it back to the company for warranty, they said the chip failed again and to check my harness, new chips free of charge( Thank Geebus).
So here are my questions, does anyone have a schematic for the fuel injectors?
IS the pin that connects to the ECU supposed to have a short to ground with 1.4k oms resistance.


To follow up that question Here are a few pictures of my top harness that connects to the ECU.
It seems like there is an awful lot of splicing going on here and IDK if that is normal please let me know thank you.
you can also see that one of the wires goes from 2 - 1.
274098
274099
274100
274101
 

·
Super Moderator
Joined
·
19,616 Posts
They aren't really rebuildable very often. Waste of money. Sad they made you waste money buying a bunch of unnecessary parts too. Buy a used ECU off ebay and clone it.
 

·
Registered
Joined
·
686 Posts
Here's the relevant part of the T8 wiring to ECU. If you need more info, WIS is a free download (link below). Note on the wiring diagram the various crimped connections (Jxx). Many are not 1-to-1 wires. 1.4 kohms is not a short. Whether it's the injector solenoid or the bulk resistance of the driver FET in the ECU (NOT the chip that was replaced) depends on what you're actually measuring.
injectors.png
WIS and EPC for Windows 10
 

·
Registered
Joined
·
10 Posts
Discussion Starter #4
Here's the relevant part of the T8 wiring to ECU. If you need more info, WIS is a free download (link below). Note on the wiring diagram the various crimped connections (Jxx). Many are not 1-to-1 wires. 1.4 kohms is not a short. Whether it's the injector solenoid or the bulk resistance of the driver FET in the ECU (NOT the chip that was replaced) depends on what you're actually measuring.
View attachment 274102
WIS and EPC for Windows 10
im measuring resistance to ground without the ECU connected, from ecu side aswell as Injector side, confirmed continuity from injector to ecu plug for good measure.
 

·
Registered
Joined
·
10 Posts
Discussion Starter #5
im measuring resistance to ground without the ECU connected, from ecu side aswell as Injector side, confirmed continuity from injector to ecu plug for good measure.
Here's the relevant part of the T8 wiring to ECU. If you need more info, WIS is a free download (link below). Note on the wiring diagram the various crimped connections (Jxx). Many are not 1-to-1 wires. 1.4 kohms is not a short. Whether it's the injector solenoid or the bulk resistance of the driver FET in the ECU (NOT the chip that was replaced) depends on what you're actually measuring.
View attachment 274102
WIS and EPC for Windows 10
also that was the exact schematic I was was looking at Shoot.
 

·
Registered
Joined
·
686 Posts
im measuring resistance to ground without the ECU connected, from ecu side aswell as Injector side, confirmed continuity from injector to ecu plug for good measure.
Are you measuring 1.4k from the ECU output pins to ground? If so, all 4 should be similar readings. You're seeing the bulk resistance of the discrete power FETs that drive the injectors. These 4 separate transistors are all driven by the same chip, which is the chip that was replaced in your ECU.
 

·
Registered
Joined
·
10 Posts
Discussion Starter #7
Are you measuring 1.4k from the ECU output pins to ground? If so, all 4 should be similar readings. You're seeing the bulk resistance of the discrete power FETs that drive the injectors. These 4 separate transistors are all driven by the same chip, which is the chip that was replaced in your ECU.
This measurement was taken from the ECU to ground and from the injector to ground, nothing connected at the end of ecu or injector. IMO the harness is bad, thoes solder connections just dont look right to me, if they are oem please let me know. so i can start diagnosing other options. (see pictures)
 

·
Registered
Joined
·
686 Posts
Everything you posted looks/sounds normal. The crimps are OEM and sealed. You said the wiring harness connections had continuity earlier.

Your ECU has failed, again. The chip that failed has nothing to do with the wiring harness because it does not switch the injectors directly. It is connected to 4 (again) separate transistors that switch the injectors. The odds of all 4 failing at the same time are near zero.
 

·
Registered
Joined
·
10 Posts
Discussion Starter #9
Everything you posted looks/sounds normal. The crimps are OEM and sealed. You said the wiring harness connections had continuity earlier.

Your ECU has failed.
just to clarify, im looking at 206a wire 2 that connects to pin 33, if i disconnect the wire at bothe ends ie fuel injector and ECU i get some continuity to ground. not a direct short but continuity. In my head there should be no connection whatsoever, am i wrong? is that a saab thing? this is my first time working on them and i have been suprised many times already.in just 2 weeks of owning it.
Also i dont mean any disrespect, but i know the ecu is bad, i sent it back they confirmed it and will repair again free of charge, im just trying to figure out why. i replaced all the things that connect to that circuit in the ecu. something caused it to fail again because it ran great for 2 weeks but then just sudden death now it wont go 20 minutes without needing to be cleared like before i sent it in.
 

·
Registered
Joined
·
686 Posts
am i wrong?
Yes. You are ignoring that there are electronics here that will measure resistance even when not powered on.
is that a saab thing?
No. You will see measurements like this in any modern car with this type of electronics driving the injectors.

The first repair on your ECU failed. If it fails again, you're better off getting another ECU as Diggs suggested, because the repair shop can't fix it properly.
 

·
Registered
Joined
·
10 Posts
Discussion Starter #11
Yes. You are ignoring that there are electronics here that will measure resistance even when not powered on.

No. You will see measurements like this in any modern car with this type of electronics driving the injectors.

The first repair on your ECU failed. If it fails again, you're better off getting another ECU as Diggs suggested, because the repair shop can't fix it properly.
ok thank you very much i appreciate the help i have been asking this question everywhere and my local saab specialist (the only one in town who works on it) said i needed a new ecu and possibly a new harness because that didint sound right and the the repair shop said look into it further incase it was not just a failed chip.
 

·
Registered
Joined
·
10 Posts
Discussion Starter #12
Okay I have more info that may muddy the water or clear up some. I took some time today and took apart the harness and disconnected a bunch of wires looking for the "short" in the process I realised. It's not the ground side that is shorting it's the positive side. So here is what I found. When I disconnect the battery I get a direct short to ground from terminal to terminal. Is that normal? In my head it dosent make sense but of course I am learning alot about electronically stuff.
 

·
Registered
Joined
·
686 Posts
Please indicate on the schematic above the points you are measuring between, and what resistances you are getting. "Terminal to terminal" is too vague to determine if there's a problem.

Remember, if the harness were bad, the car wouldn't have worked for two weeks after reinstalling ECU.
 

·
Registered
Joined
·
10 Posts
Discussion Starter #14
Please indicate on the schematic above the points you are measuring between, and what resistances you are getting. "Terminal to terminal" is too vague to determine if there's a problem.

Remember, if the harness were bad, the car wouldn't have worked for two weeks after reinstalling ECU.
Battery terminal to battery terminal. Ground to +.
And the 1.5k resistance to ground I was referring to erlier was actually not the ground it was the J45 side of the harness.
 

·
Registered
Joined
·
686 Posts
What is the NUMBER of ohms you are measuring across the battery terminals? What are you measuring with? A DMM (digital multimeter)?

EDIT: Also REVERSE the probes and tell me the NUMBER of ohms you read with the probes that way.
 

·
Registered
Joined
·
10 Posts
Discussion Starter #16
Here are some Photos of everything you asked for. First 2 are Ohms and their respective polarity and second 2 are continuity, note both polarity beeped indicating continuity.
What is the NUMBER of ohms you are measuring across the battery terminals? What are you measuring with? A DMM (digital multimeter)?

EDIT: Also REVERSE the probes and tell me the NUMBER of ohms you read with the probes that way.
20200620_230144.jpg
20200620_230123.jpg
20200620_230158.jpg
20200620_230223.jpg
 

Attachments

·
Registered
Joined
·
2,018 Posts
just replace ur ECU, If u have a short in the wiring harness the issue will become apparent the moment u install the ecu.
I have not seen a successful T8 repair, until i see one with my own eyes then i will start believing in them, specially the injector chip repair which i tried myself not only once, but 4 times ..
 

·
Registered
Joined
·
686 Posts
Note the negative readings in your first and third pics. Negative resistance is impossible in a circuit that isn't powered up.

There are more than 30 computers in this car, and at least half a dozen that get battery voltage at all times. These have capacitors in them that retain voltage for a time after you disconnect the battery. Watch the voltage between the battery terminals with your meter after disconnecting battery and you'll see it drop down, but it takes a while to get to zero.

Even when the car is at zero volts on the battery terminals, you will measure different resistances simply by reversing the meter probes. One reason is that the meter puts out voltage when measuring resistance, and will charge any capacitors in the circuit, like the ones mentioned above. This is why you wait for the resistance reading to stabilize when measuring circuits containing capacitors. Another reason is that you will get different readings with semiconductors (diodes are the simplest kind) in the circuit when you reverse the probes. Both of these are why the the WIS only recommends using an ohmmeter like this to test for shorts to ground and for open wires in a harness, after isolating the circuit by pulling its fuse.

A short (or continuity) is 1 ohm or less in these kinds of measurements. A open is infinite ohms. Your meter may well indicate a "short" on anything less than 40-50 ohms in its continuity test. An "open" is considered to be anything above that by your meter. That makes sense when you're troubleshooting 120/240VAC power wiring, but not necessarily here.

TL;DR If these readings were real, you're get quite a large, bright arc when connecting the battery, not to mention the car would not work at all. The spark you do get when you connect the battery is all those little capacitors charging up when the computers restart.
 

·
Registered
Joined
·
686 Posts
just replace ur ECU, If u have a short in the wiring harness the issue will become apparent the moment u install the ecu.
I have not seen a successful T8 repair, until i see one with my own eyes then i will start believing in them, specially the injector chip repair which i tried myself not only once, but 4 times ..
Was gonna post in the other thread on this. It will be less confusing to OP to take this back there.
 

·
Registered
Joined
·
10 Posts
Discussion Starter #20
Clearly I have no understanding of how car electronics work lol. Okay I'll look into getting a new cpu next month when I have the funds.
 
1 - 20 of 25 Posts
Top