VZ V6 5Auto Hot relays please help

[Decksta]

Hey guys,

Accessory's relay, ignition relay, under dash and the engine control relay under bonnet have all over heated.

Was after a 3.5 hour drive ran like a dream, then I went to restart it after 30mins off and she would not start came up with the svs low fuel etc. typical of a ecu unit failure, anyway after a full night off she started no worries in the morning, but after about 20mins and I turned it off into shops then out again failed again and would not start. so I swapped the relays around with unburnt ones and she fired up so I drove home 3.5hours as quick as I could, but the relays still got hot had a infa temp outside cover hit 100c, but ran like a dream again all way home.

So today I pulled every fuse out and relay and went through all of them to see when it trigged the relays to over heat.

The only ones left in were the acc relay, ign relay and engine control relay the ones that got hot, with key on acc and the 7.5amp ignition fuse in, all those relays would start to heat up.
I also tried removing the ing relay and the EC relay and the acc relay would still heat up on its own.
Would also heat up with the key on ing.
As soon as I removed the 7.5amp ignition fuse they would cool off tested current 6amps going through but varied. still not enough to heat up relays and those size relays would handle 40amps constant yes?
no other relays got hot or changed temp at all

So after searching here all day thought it would be the ecu so I disconnected it and re did test and they still got hot.

batt fine 12.5v and 7 months old alt charges upto 14.3v

so could it be the bcm? not sure how as everything still functions perfectly. does it run any sensors through it? im guessing its drawing some amps but not sure how as I pulled everything else out and the batt doesn't drop voltage enough as it gets down to 12.2v only so that's telling me maybe 10-20amps? not enough to heat up relays.

I'm fairly well mechanical and electrical knowledge but this has got me stumped. any help will be appreciated.

 

[Decksta]

Here is a pic of the burnt relays and the fuse

 

[K-BAGZ]

Check all your ground earths and main fuses. And also check your battery leads and terminals. Wouldn't hurt to clean/blow out the fuse blade holders with contact cleaner. You'd be surprised how much a small amount of dirt can do to an electrical circuit.

Take your time and work slowly.

 

[diysv6]

This is some numbers from my SV6.

Might help you through your problem.

http://forums.justcommodores.com.au/vz-holden-commodore-2004-2006/241174-vz-1tonne-v6-manual.html

 

[Decksta]

Guys update (been away for awhile)

Went through and cleaned all the terminals and earth points checked the resistance on the earth points and they are all good checked terminals etc.

powered the relays from a separate batt and hit 90c on the coil with cover removed, also tried a new diff type one out of box and coil hits 75c

had code (U0100) stored in the car were it loses comms between pcm and bcm etc but hasn't done that again

Relay power

Batt power 12.2v

Accessory relay

Trig/switch 160mA
Accessory 40mA
Volt on switch 12.1v

Ignition relay

Trig/switch 160mA
Accessory 840mA
Volt on switch 12.05v

Engine control relay

Trig/switch 160mA triggers when key to accessory position
Accessory 300mA initial buzz sound, 30mA after 10secs buzz sound gone, key to ignition still 30mA, key to off takes 5secs to turn off.
Volt on switch pin 10.85v < only one different
Volt on Accessory pin 12.1v relay off 11.98v relay on

not sure where to go now, except test when car running on engine control relay to see if volt on switch pin comes up,

is there anything that the tech 2 can do to test the condition of the BCM or PCM?

 

[diysv6]

Here are my thoughts if they can help you out. I think you are confident around the wiring/relay areas in the car.

But as Murphy says - things can happen.
Could an incorrect relay have been plugged into the car's relay sockets during your research and caused wiring damage? eg a battery powered burn through in the wiring loom/s?

" powered the relays from a separate batt and hit 90c on the coil with cover removed, also tried a new diff type one out of box and coil hits 75c" .
Did you find out why the temperatures are so different? Ohmic resistance of all coils should be the same or within reasonable limits. Shorted turns?

Looking at my Haynes 41743 Manual, the relays in the Interior fuse box - Accessory and Ignition control are the same, and are the same as the Ignition Control and Start Relay in the under bonnet relay/fuse box. If you are using Haynes as an information source is it correct? The normal 4 pin relay from various after market suppliers does not necessarily match up to the pin-out functions of the Holden relays. (I bought relays for my VZ before a long trip (as backup), and when I tested them for pin-out compatibility they were different - ended up buying the Holden relays).

Also, are all of the relays you are swapping not faulty. Shorted turns, ohmic resistance correct, there is DC isolation between the coil windings and the contact sets.

Engine control relay
Trig/switch 160mA triggers when key to accessory position
Accessory 300mA initial buzz sound, 30mA after 10secs buzz sound gone, key to ignition still 30mA, key to off takes 5secs to turn off.
Volt on switch pin 10.85v < only one different
Volt on Accessory pin 12.1v relay off 11.98v relay on

I sometimes hear a high frequency noise from the engine area when I turn on the ignition if the bonnet is up. I think it might be the Throttle Body going through a "test" sequence. The accessory current draw could be the Blaupunkt CD deck/radio/aerial setting up.

The lower voltage of 10.85V could be the source of your car's failing when hot. Can you trace it back to other connectors, distribution points etc.?

Engine control relay (under bonnet).
Terminal 85 should be 12v feed through the Engine fusible link (60A) and virtually not change as various loads are applied when the car is started up. Is the fusible link in good condition? If these links get close to the melting point are they deemed as damaged and must be replaced? The Main, Engine and lighting are all 60Amps. Have you tried a swap of the lighting link to the engine link etc?

Terminal 86 goes to the ECU X2 -24. and is 10.85V?
When the ignition is on and engine running I would expect the voltage to be less than 1.0volt, as a transistor switch in the ECU would be switched on hard to operate the Engine Control relay coil. If the voltage does not change or is erratic, then a wiring fault, dirty connector or an ECU fault could be present. If the static (transistor) switch is not operating properly, then the voltage on Terminal 86 could vary from 12V to about 0.5V or less. This would cause the Engine Control relay to drop out. Maybe when the ECU cools down, the static switch comes good and the car is drivable.

When my ECU failed it took weeks before the ECU switching transistor for a fuel injector coil died full time, and I could locate the problem.
Hope yours is a simple wiring fault.

 

[Decksta]

Here are my thoughts if they can help you out. I think you are confident around the wiring/relay areas in the car. < thanks appreciate your thoughts

But as Murphy says - things can happen.
Could an incorrect relay have been plugged into the car's relay sockets during your research and caused wiring damage? eg a battery powered burn through in the wiring loom/s?

No same part numbers and from vz i.e. fan lights etc. and tried diff relay from vx

" powered the relays from a separate batt and hit 90c on the coil with cover removed, also tried a new diff type one out of box and coil hits 75c" .
Did you find out why the temperatures are so different? Ohmic resistance of all coils should be the same or within reasonable limits. Shorted turns?

Yes sorry the other different relay I tried had different resistor across the coil

Looking at my Haynes 41743 Manual, the relays in the Interior fuse box - Accessory and Ignition control are the same, and are the same as the Ignition Control and Start Relay in the under bonnet relay/fuse box. If you are using Haynes as an information source is it correct? The normal 4 pin relay from various after market suppliers does not necessarily match up to the pin-out functions of the Holden relays. (I bought relays for my VZ before a long trip (as backup), and when I tested them for pin-out compatibility they were different - ended up buying the Holden relays).

not using Haynes have vx manual workshop manual asked Holden for the circuit diagrams and I know there is a difference, anyway yes those relays are the same match the part numbers

Also, are all of the relays you are swapping not faulty. Shorted turns, ohm resistance correct, there is DC isolation between the coil windings and the contact sets.

All match ohms resistance, yes no continuity between contacts

Engine control relay
Trig/switch 160mA triggers when key to accessory position
Accessory 300mA initial buzz sound, 30mA after 10secs buzz sound gone, key to ignition still 30mA, key to off takes 5secs to turn off.
Volt on switch pin 10.85v < only one different
Volt on Accessory pin 12.1v relay off 11.98v relay on

I sometimes hear a high frequency noise from the engine area when I turn on the ignition if the bonnet is up. I think it might be the Throttle Body going through a "test" sequence. The accessory current draw could be the Blaupunkt CD deck/radio/aerial setting up.

Yes amp draw directly rated to that noise, pulled all fuses for test so as not to detect any other systems

The lower voltage of 10.85V could be the source of your car's failing when hot. Can you trace it back to other connectors, distribution points etc.?

I have little trouble with this a bit as + power is from batt through fuse(which has no resistance but I should check when warm) its grounded out via BCM or PCM to make circuit its not low enough to drop the relay off though, hard to check resistance as its not stable and of course its hard to test as needs to be hooked up and powered to test i.e. pcm running

Engine control relay (under bonnet).
Terminal 85 should be 12v feed through the Engine fusible link (60A) and virtually not change as various loads are applied when the car is started up. Is the fusible link in good condition? If these links get close to the melting point are they deemed as damaged and must be replaced? The Main, Engine and lighting are all 60Amps. Have you tried a swap of the lighting link to the engine link etc?

no I should test after being warm against all

Terminal 86 goes to the ECU X2 -24. and is 10.85V?
When the ignition is on and engine running I would expect the voltage to be less than 1.0volt, as a transistor switch in the ECU would be switched on hard to operate the Engine Control relay coil. If the voltage does not change or is erratic, then a wiring fault, dirty connector or an ECU fault could be present. If the static (transistor) switch is not operating properly, then the voltage on Terminal 86 could vary from 12V to about 0.5V or less. This would cause the Engine Control relay to drop out. Maybe when the ECU cools down, the static switch comes good and the car is drivable.

I would have to check over the PCM to see the voltage, but I should have tested that so I will now

When my ECU failed it took weeks before the ECU switching transistor for a fuel injector coil died full time, and I could locate the problem.
Hope yours is a simple wiring fault.

good to know I will have to take it for a long drive to see if it replicates it, going to be hard driving for long time in circles though as I don't want to be to far away for a tow, its looking less likely to be a wiring fault, hate the fact it could be an intermitted problem but it usually surely is. thanks for your help I will look into your suggestions and test some more when hot.

 

[diysv6]

Hi Decksta,

Some ideas to maybe save you time.

Can you use a hair drier - carefully - on the ECU to bring on the fault while in the workshop? Being prudent I would not exceed 45c on the heatsink as the heatsink is cooled by air flow. Heat soak under the bonnet after a good run gets around 50c.

I have used wife's dress making pins to punch through wire insulation, eg in your case near the relay block under the bonnet, terminal 86, and hook up to a DMM and monitor voltages in the cabin whilst heating up the ECU and later driving around. Note: Treat the DMM screen as a mobile phone whilst on the road - ...................

The DMM is not ideal to show intermittent changes in voltage but if it changes and reads stupidly, then the circuit back to the ECU could be breaking down or the ECU is failing.
Also a changing voltage could also be caused by the fusible link and circuitry before the Engine Control relay.
You will need to establish that the 12V feed to the relay and through the coil winding to terminal 86 is trouble free.
More dressmaking pins set into the wiring before pin 85 will give you extra sampling points in your fault chasing.

Looking at Haynes, the engine control relay does have some DTCs.
P0685 Engine Control relay open circuit
P0686 Engine Control relay circuit low
P0687 Engine Control relay circuit high


If you can get a DTC reader on the car you may pickup these codes. This would indicate an ECU/relay coil problem.
(Super Cheap Auto have a trouble code reading service for about $20 to $30 at some dealers).

Hope this helps.

 

[Mitchyboy]

I just got the same problem.
Did u find what the cause was.
As its got me stumped too

 

[Darren Holt]

On a Totally Different Subject...
My VZ has now just done 250,000Kms
Can i Change my Oil Grade from the Original 5W30 to 10W40 Synthetic?
As I have developed some Minor Oil Leaks and want to Minimise this.
I am Having the 4 Front Cam Oil Seals Replaced on Monday the 3rd
Darren