2003 XC90 T6 intermitted won't start,new starter & battery

[cocoli2007]

Originally Posted by SwissXC90

My vote is still the start inhibit switch on the auto gearbox

Pin C:28 on the CEM, a BL-Y wire heading to switch 8:37 on the auto gearbox

Pin C:28 is switched to ground
Not sure of the logic: either C:28 is grounded to inhibit start, or to enable start. One or the other.

But worth checking this

If the gearbox is not in P or N you cannot start the engine and the symptoms are identical to your descriptions. No messages are shown, no clicks are heard from the starter, nothing happens when key is in PosIII.

Check by trying to turn off ignition and remove key WITHOUT touching the gearbox level at next failled start attempt. If you CANNOT remove the key, the car thinks the gearbox is in something other than P or N, thus preventing key removal and preventing start.

No problem to remove the key. The car worked for 1 week and totally stopped today, I had to use wire to connect starter relay pin 30 & 87 to start it.

Can Vida reset/reload CEM/ECM? If yes, maybe I go to buy it on ebay ($60).

Thanks.

[SwissXC90]

Originally Posted by cocoli2007

Can Vida reset/reload CEM/ECM? If yes, maybe I go to buy it on ebay ($60).

Reset: Yes, easy
Tell you fault codes and history: Yes, easy
Tell you fault finding procedure: Yes

Reload: Only possible with active dealership subscription

But reloading firmware to a device doesn't fix problems like this.

[cocoli2007]

Originally Posted by SwissXC90

Reset: Yes, easy
Tell you fault codes and history: Yes, easy
Tell you fault finding procedure: Yes

Reload: Only possible with active dealership subscription

But reloading firmware to a device doesn't fix problems like this.

I borrowed DIVA-Dice 2014A, it does not show any errors on CEM/ECM, only BCM has several errors. I am very disappointed it has CCM calibration function. I see there is 'reset' option for CEM, I click it, nothing happened.

All of above mess (AC/fan always start automatically when start the car, and start failure intermittently) was caused after disconnected battery, I feel something is wrong on software.

[SwissXC90]

Get VIDA again and print a fresh list of all errors and report them here.
Each error has a frequency report - are they intermittent of constant?
Print all errors from all control modules to PDF and then clear them and see what reappears.

You can reset the entire vehicle in VIDA - under Software -> Advanced -> Reset

[cocoli2007]

Originally Posted by SwissXC90

Get VIDA again and print a fresh list of all errors and report them here.
Each error has a frequency report - are they intermittent of constant?
Print all errors from all control modules to PDF and then clear them and see what reappears.

You can reset the entire vehicle in VIDA - under Software -> Advanced -> Reset

Thanks again.

Here are 3 alerts, they come back immediately after erase.

These days, I had to use bypass wire to start my car very time. There is a strange behavior, first time bypass start always failed, turn off and turn on car again, try bypass start, then it works.

It is so weird, under CCM 'advance' tab, I only see 4 options, not like others 6 option. There is no 'calibration' option, is it normal, or dice firmware out-of-date, or 2003 XC90 has not such option. But dealer can do calibration for CCM for me.

Regards.

[SwissXC90]

You photos show part of the story.
For a full fault description it is important to see the faul frequency, open each fault code in VIDA to lookl at the details, and print them to PDF, and then post the results here.

Anyway, good news: Ignore the CCM code, the failled AQS has nothing to do with your problem whatsoever.

And the other good news:
You have TCM communication issues, that definitely is related to your problem
If the Transmission Control Unit cannot talk to the ECM and CEM, then many things won't work properly. And it would not suprise me that a no start condition is one of them.

The TCM is connected directly to the ECM via high speed CAN bus.
The ECM is then connected to the CEM.

You need to investigate your TCM issues resolve them.
It could be a number of things:

• Corrosion in TCM connector or ECM connector, focus especially on the pins related to the high speed can bus wires, because a CAN bus break results in no communication
• TCM has no power
• TCM has bad ground
• Wiring break or short in the high speed CAN bus to TCM
• Corrosion inside TCM module
• Faulty TCM module
• Faulty CEM module
• Corrosion on CEM high speed CAN bus wires (although you would loose other high speed devices as well)

Unfortunately corrosion on CEM connector is quite common on older cars. Best is to ddisconnect connectors and inspect. Carefully. And clean with contact cleaner afterwards.

If any sign of corrosion in the TCM or the CCM module, get it repaired or replaced.

You can also deduce much more by looking at the fault code frequency and the frozen parameters stored when the fault occured.
The best thing to do is print the entire vehicles fault codes and full details to PDF, then you have a fixed snapshot of the problem and can analyse it without having VIDA connected.

[SwissXC90]

I need to know what engine and gearbox you have, the wiring is slightly different.

Eg: for TF-80SC gearbox the TCM is connected to a branch 53/353 on the high speed can loom, which also goes to CEM and BCM. So if that is the case, the fault cannot be CEM or on the bus between CEM and BCM, as BCM is happy.
So focus on the TCM and loom from branch 53/353

Further tips:
Measure the CAN bus on the TCM connector, both Hi and Lo wires.
Check the power and ground
Open the TCM and look for corrosion
Replace the TCM with a known good unit

If my comments are too technical for you, then take the vehicle to an expert

[cocoli2007]

Originally Posted by SwissXC90

I need to know what engine and gearbox you have, the wiring is slightly different.

Eg: for TF-80SC gearbox the TCM is connected to a branch 53/353 on the high speed can loom, which also goes to CEM and BCM. So if that is the case, the fault cannot be CEM or on the bus between CEM and BCM, as BCM is happy.
So focus on the TCM and loom from branch 53/353

Further tips:
Measure the CAN bus on the TCM connector, both Hi and Lo wires.
Check the power and ground
Open the TCM and look for corrosion
Replace the TCM with a known good unit

If my comments are too technical for you, then take the vehicle to an expert

My car is 2003 XC90 T6, I will take my car to a mechanical (who only focus on electric part) later this after.

What I found from wiring diagram starter system is, CEM and Ignition switch is connected via connector "4", CEM and TCM connected via connector "4", but I don't find where connector "4" is? Bundle of ignition switch wires go to hood directly, I did not see connector near CEM.

CEM is in good shape, only a few relays have corrosion (not so bad), mother board is pretty clean, I cleaned relays already, but does not help.
I will run diagnosis again and post detail info.

[SwissXC90]

Originally Posted by cocoli2007

My car is 2003 XC90 T6, I will take my car to a mechanical (who only focus on electric part) later this after.

What I found from wiring diagram starter system is, CEM and Ignition switch is connected via connector "4", CEM and TCM connected via connector "4", but I don't find where connector "4" is? Bundle of ignition switch wires go to hood directly, I did not see connector near CEM.

CEM is in good shape, only a few relays have corrosion (not so bad), mother board is pretty clean, I cleaned relays already, but does not help.
I will run diagnosis again and post detail info.

You don't say what transmission you have
Do you have AW55-50SN/AW50AWD or the 4T65AWD?

I would not call any sign of corrosion "good shape". Whereever you find visible corrosion, there always exists non-visible corrosion

I don't have a 2003 wiring diagram here, the earliest I have is 2005
Ignition switch 3/1 is connected directly to CEM 4/56

Anyway, take it to an expert and good luck.

[diro]

Oh dear...
You guys going deeper to the woods where obviously are too many trees there. Dont get lost

There is starting system diagram in front of you so why dont start from the simple thing/fault - intermitent voltage supply to the starter motor relay pin 86 as I suggested before?
Get a wire, connect it directly from terminal 50 (ignition switch) to the starter motor relay pin 86 and CEM pin A20. This way you will bypass harness connector and supply voltage to the relay and CEM pin A20 which is on the same circuit. Try it for another week or 2 and see how it goes.

Personally I would not do this way - I'd rather check harness from relay/fuses box having a multimeter in my hand. It maybe would take me more time but thats the way I work every day with car electrics/electronics/diagnostics/programming.

Again:
ignition switch terminal 50 has constant 14.2volts but starter motor relay terminal 86 has intermitent 14.2v supply.
We cant rule out CEM pin A20 also gets 14.2v intermitently if the wire is broken somewhere or harness connector is corroded etc.
If CEM wont get constant 12v (14.2v) potentially this can cause communication faults etc.

P.S. I reply and share my thoughts only based on the information and fault description provided in this thread.