Technical Another u1700 problem!

[Norrby89]

Hello everyone.

I have for almost a year had a stilo 2001 with the 1.6 engine and im really happy with it until this week.

Started the car om Monday and i had a Christmas tree and no gauges is working. Car stil runs great and i just have a bt connection to my phone for speed and fuel level. Only code im geting is u1700 no other Codes.

But it would be really nice to fix this issue, i have checked the D4 connector and it looks like it is brand new inside. Have checked a little bit on the wire then self but everything looks fine.

So if i want to try and measure the D4 is there any specific pins that i need to check? Have looked for a diagram but in unsure if there is a difference between different years and engines.

 

[Mike1alike]

Hi and Welcome to the forum!

U1700 = CAN communication fault (Body ↔ Instrument cluster).
That’s why you get the Christmas tree + dead gauges but the engine runs fine.
What to check on D4 connector (behind dash / cluster)
You’re mainly interested in power, ground, and CAN lines.
1. Power & ground (most common cause)
Check permanent +12 V
Check ignition-switched +12 V
Check grounds (very important).
Measure voltage drop, not just continuity:
Key ON
Load on (lights ON)
Ground should be < 0.2 V drop
Bad grounds are very common on early Stilo.
2. CAN lines
CAN High and CAN Low at D4
With ignition OFF, measure resistance between CAN-H and CAN-L
Expected ≈ 60 Ω
120 Ω = one terminator missing
Open / unstable = wiring or module fault
With ignition ON:
CAN-H ≈ 2.5–3.5 V
CAN-L ≈ 2.5–1.5 V
They should be mirror images
3. Wiggle test While monitoring:
CAN voltages
Cluster power feed
Wiggle:
D4 connector
Loom near steering column
Fuse box area
If gauges flicker → wiring/connector fault confirmed.
Important Stilo-specific notes
Cluster itself is a known failure point (dry joints)
U1700 with no other codes often = cluster losing CAN or ground
Year/engine doesn’t matter much — CAN wiring is the same
If wiring checks out
Next step:
Remove cluster
Inspect / reflow solder joints (especially CAN transceiver & power pins)
Or swap with known-good cluster for test
Bottom line
Start with:
Grounds
Power feeds to cluster
CAN resistance (60 Ω test)
Most Stilos with this symptom are ground or cluster-related, not ECU.

If you want, I can tell you exact pin numbers once you confirm:
Left or right-hand drive (presume left)
Analog or digital cluster.

 

[Norrby89]

Hi and Welcome to the forum!

U1700 = CAN communication fault (Body ↔ Instrument cluster).
That’s why you get the Christmas tree + dead gauges but the engine runs fine.
What to check on D4 connector (behind dash / cluster)
You’re mainly interested in power, ground, and CAN lines.
1. Power & ground (most common cause)
Check permanent +12 V
Check ignition-switched +12 V
Check grounds (very important).
Measure voltage drop, not just continuity:
Key ON
Load on (lights ON)
Ground should be < 0.2 V drop
Bad grounds are very common on early Stilo.
2. CAN lines
CAN High and CAN Low at D4
With ignition OFF, measure resistance between CAN-H and CAN-L
Expected ≈ 60 Ω
120 Ω = one terminator missing
Open / unstable = wiring or module fault
With ignition ON:
CAN-H ≈ 2.5–3.5 V
CAN-L ≈ 2.5–1.5 V
They should be mirror images
3. Wiggle test While monitoring:
CAN voltages
Cluster power feed
Wiggle:
D4 connector
Loom near steering column
Fuse box area
If gauges flicker → wiring/connector fault confirmed.
Important Stilo-specific notes
Cluster itself is a known failure point (dry joints)
U1700 with no other codes often = cluster losing CAN or ground
Year/engine doesn’t matter much — CAN wiring is the same
If wiring checks out
Next step:
Remove cluster
Inspect / reflow solder joints (especially CAN transceiver & power pins)
Or swap with known-good cluster for test
Bottom line
Start with:
Grounds
Power feeds to cluster
CAN resistance (60 Ω test)
Most Stilos with this symptom are ground or cluster-related, not ECU.

If you want, I can tell you exact pin numbers once you confirm:
Left or right-hand drive (presume left)
Analog or digital cluster.

Thank you!

This is to be honest amazing! Was totally fixed on that it was communication between the ecu and body computer so i have only checked the D4 connector under the fuse box at the Battery.

I also have lost central locka and power Windows that i forgot to write in my first post if that makes any difference? Can it be a bad body computer or is that normal when you get a bad connection to the cluster?

Would be really amazing if i could get the exact pin numbers or if there is a diagram for it.

 

[Mike1alike]

Ah, that extra info changes things a lot.
Loss of central locking + electric windows + dead cluster + U1700 points very strongly in one direction.
Key clarification first
You checked the D4 connector under the battery/fuse box.
That’s Body Computer (BCM) related, not the instrument cluster connector.
So you weren’t wrong, you were just looking in the wrong place for the symptom.
What the added symptoms tell us
When you lose at the same time:
Instrument cluster (gauges + warning lights)
Central locking
Power windows
→ This is NOT a cluster-only fault
This is Body Computer power/ground or CAN distribution failure.
The cluster is only a victim here.

Most likely causes (in order):
1. Body Computer power or ground fault (VERY common on Stilo)
Corroded or loose BCM ground
Voltage drop on BCM supply
Water ingress/condensation near fuse box
Battery area wiring damage (acid vapour + moisture)
This perfectly explains:
U1700
Intermittent recovery
Windows + locks gone
Cluster offline
2. CAN splice / joint issue
CAN bus is daisy-chained through the BCM
If BCM loses power/ground → CAN collapses → U1700 everywhere
3. BCM internal fault
Less common than people think — rule out wiring first.

Important correction
“Is that normal when you get a bad connection to the cluster?”
No!
A bad cluster connection does NOT kill windows or central locking.
Those are BCM-controlled functions.

Exact checks and pin info (what you asked for)
Body Computer connectors (under dash/fuse box, NOT battery D4)
You want the BCM main connectors, usually labelled: A, B, C
(Colour varies by year)
Critical pins to check
Power
Permanent +12 V
Ignition-switched +12 V
Expect:
Battery voltage
No drop when load applied (lights, blower)
Grounds (MOST IMPORTANT)
Check continuity AND voltage drop to chassis:
Expect < 0.1–0.2 V drop under load
Bad BCM grounds cause exactly your symptoms.
CAN
CAN High / CAN Low
Ignition OFF → ~60 Ω between H and L
Ignition ON:
CAN-H ≈ 2.5–3.5 V
CAN-L ≈ 2.5–1.5 V
If CAN collapses when BCM loses power → everything dies.

Where to physically look (very important)
On the Stilo 2001:
Under-dash fuse box/BCM area
Wiring loom behind and above the fuse box
Ground points behind kick panels
Battery tray & bulkhead wiring (acid damage is common).

Do a wiggle test while watching:
Cluster wake up
Windows suddenly work
Locks respond
That confirms wiring/ground 100%.
Is there a diagram?
Yes — eLearn has:
BCM connector pinouts
CAN routing
Ground locations
If you tell me:
LHD or RHD
Manual or automatic
I’ll tell you exact BCM connector + pin numbers to probe first, so you don’t waste time.

Bottom line
This is not ECU vs BCM communication
This is BCM losing power/ground or CAN intermittently
Fix that, and:
U1700 disappears
Cluster comes back
Windows & locks return
You’re very close already — you just need to move from the battery D4 to the BCM itself.

 

[Norrby89]

Ah, that extra info changes things a lot.
Loss of central locking + electric windows + dead cluster + U1700 points very strongly in one direction.
Key clarification first
You checked the D4 connector under the battery/fuse box.
That’s Body Computer (BCM) related, not the instrument cluster connector.
So you weren’t wrong, you were just looking in the wrong place for the symptom.
What the added symptoms tell us
When you lose at the same time:
Instrument cluster (gauges + warning lights)
Central locking
Power windows
→ This is NOT a cluster-only fault
This is Body Computer power/ground or CAN distribution failure.
The cluster is only a victim here.

Most likely causes (in order):
1. Body Computer power or ground fault (VERY common on Stilo)
Corroded or loose BCM ground
Voltage drop on BCM supply
Water ingress/condensation near fuse box
Battery area wiring damage (acid vapour + moisture)
This perfectly explains:
U1700
Intermittent recovery
Windows + locks gone
Cluster offline
2. CAN splice / joint issue
CAN bus is daisy-chained through the BCM
If BCM loses power/ground → CAN collapses → U1700 everywhere
3. BCM internal fault
Less common than people think — rule out wiring first.

Important correction
“Is that normal when you get a bad connection to the cluster?”
No!
A bad cluster connection does NOT kill windows or central locking.
Those are BCM-controlled functions.

Exact checks and pin info (what you asked for)
Body Computer connectors (under dash/fuse box, NOT battery D4)
You want the BCM main connectors, usually labelled: A, B, C
(Colour varies by year)
Critical pins to check
Power
Permanent +12 V
Ignition-switched +12 V
Expect:
Battery voltage
No drop when load applied (lights, blower)
Grounds (MOST IMPORTANT)
Check continuity AND voltage drop to chassis:
Expect < 0.1–0.2 V drop under load
Bad BCM grounds cause exactly your symptoms.
CAN
CAN High / CAN Low
Ignition OFF → ~60 Ω between H and L
Ignition ON:
CAN-H ≈ 2.5–3.5 V
CAN-L ≈ 2.5–1.5 V
If CAN collapses when BCM loses power → everything dies.

Where to physically look (very important)
On the Stilo 2001:
Under-dash fuse box/BCM area
Wiring loom behind and above the fuse box
Ground points behind kick panels
Battery tray & bulkhead wiring (acid damage is common).

Do a wiggle test while watching:
Cluster wake up
Windows suddenly work
Locks respond
That confirms wiring/ground 100%.
Is there a diagram?
Yes — eLearn has:
BCM connector pinouts
CAN routing
Ground locations
If you tell me:
LHD or RHD
Manual or automatic
I’ll tell you exact BCM connector + pin numbers to probe first, so you don’t waste time.

Bottom line
This is not ECU vs BCM communication
This is BCM losing power/ground or CAN intermittently
Fix that, and:
U1700 disappears
Cluster comes back
Windows & locks return
You’re very close already — you just need to move from the battery D4 to the BCM itself.

Hello did ofcource not have time during the weekend to check anything.

But the car is LHD and manual, have checked a little bit in Elearn but just found the page with all the pins for all the connectors but i cant realy find a main power and ground pins, just some signal ground and so on.

 

[Mike1alike]

That’s normal in eLearn — it doesn’t label them as “main power” and “main ground” in an obvious way.
On the Stilo, the instrument cluster does NOT have one single big +12 V and one big ground like older cars. Power and ground are distributed.
Important first clarification
U1700 + dead gauges + no central locking + no electric windows = Cluster is losing its power/ground or CAN reference, not an ECU-engine issue.
So you’re right to stop chasing D4 alone.
Where the cluster actually gets power & ground
Instrument cluster connectors
The cluster is fed by multiple pins, usually split into:
Permanent battery + (via Body Computer)
Ignition + (MAR)
Multiple grounds (shared with BCM)
In eLearn these are shown as:
“+30” = battery positive
“+15” = ignition switched positive
“Massa” / “GND” / “Signal ground” = ground
There is no single pin called “MAIN GROUND” — that’s the confusing part.
What to measure (this is the key bit)
Forget signal grounds for now. Do this instead:
1. At the instrument cluster connector
With connector plugged in (back-probing if possible):
Check +30 pin → chassis ground
→ must be 12–12.6 V all the time
Check +15 pin → chassis ground
→ must be 12 V with key in MAR
Check ground pins → battery negative
→ must be < 0.5 Ω
If any of these drop out when the fault is present → you’ve found it.
2. Body Computer (this is VERY important)
Loss of central locking, power windows, cluster communication points strongly to BCM power or ground, not the cluster itself.
Check BCM battery feeds and BCM grounds.
Especially:
Ground point behind dashboard / A-pillar
Ground under battery tray
Ground near steering column.
A slightly bad BCM ground can kill gauges, throw U1700, make CAN look “dead”.
Why D4 looked “fine”
D4 is CAN lines only. CAN can look perfect electrically while:
BCM has bad ground
Cluster loses ignition feed
Voltage collapses under load
That’s why this fault fools people.
Is a bad Body Computer possible?
Yes — but rare. 90% of the time on Stilo this is:
Corroded ground splice
Loose BCM ground
Battery tray ground rot
Dash earth point oxidised.
Only suspect the BCM after confirming:
All +30 and +15 are stable
Grounds stay <0.5 Ω under load

 

[Mike1alike]

And I just discovered on my Punto that BCM ground is located on the chassis next to left headlight.
There are multiple wires (8) connected in 2 crimps to one ring and it sits next to left headlight. It's important to clean that ring and connection surface on chassis. I think headlights ground is in there too.
This is mine, I just cleaned it yesterday.

 

[Norrby89]

And I just discovered on my Punto that BCM ground is located on the chassis next to left headlight.
There are multiple wires (8) connected in 2 crimps to one ring and it sits next to left headlight. It's important to clean that ring and connection surface on chassis. I think headlights ground is in there too.
This is mine, I just cleaned it yesterday.

Did find a similar point on my stilo but everything thing looked fine on it.

Started looking and i did manage to get rid of the problem by removing a aftermarket alarm module and after that disconecting the battery negative for a few min.

Now everything is working once more, but i so not know if the alarm module have anything to do with it or if it was just disconecting the negative pole that did it.

 

[Mike1alike]

Now everything is working once more, but i so not know if the alarm module have anything to do with it or if it was just disconecting the negative pole that did it.

Yes, either one of the two, alarm module or disconnecting battery feed could have done it.
If the alarm module was the one causing the problem, I'd say that cleaning its pins and contacts on plugs connected to it should fix it.
Also, there is one important thing for you to check, state of the battery. State of health, internal resistance and state of charge. Bad/discharged battery can be the fault.

 

[Norrby89]

Yes, either one of the two, alarm module or disconnecting battery feed could have done it.
If the alarm module was the one causing the problem, I'd say that cleaning its pins and contacts on plugs connected to it should fix it.
Also, there is one important thing for you to check, state of the battery. State of health, internal resistance and state of charge. Bad/discharged battery can be the fault.

Car starts and runs without the module so i will just keep it disconected and dont have any fob for it so i guess it's might not have been connected properly.

Battery i will change at a later stage anyway since it probably got a bit degraded when my generator died last summer.

 

[Mike1alike]

Battery i will change at a later stage anyway since it probably got a bit degraded when my generator died last summer.

That is a long time, sience last summer. It could be degraded, running them discharged is what kills them quickly, internal resistance increases quickly in that case. How old is the battery. Have it tested if you can, with one of those dedicated battery testers that tell SOH, SOC, IR. Then you'll know for sure what state's it in.
If IR is good (less than 6 mΩ is perfect, 6-9 mΩ is good, more than 9mΩ not good) recharging it can give it more years of service. Especially recharging on 'Repair/Pulse' mode on these modern chargers after first slowly discharging the battery with a 21W bulb light, to no less than 10.5 V.