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Electrical questions

cgalpha08

cgalpha08

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So the power mirrors and dome lights do not work in my H3. I first thought the power mirror switch on the door might be bad so I replaced it, didn't work. After taking the door panel apart I tested the connections and discovered that there is no power going to the power mirror part of the wiring harness, and none going to the motor behind the mirror. The dome lights, I pulled apart the A pillar trim, there is power to the sunroof and the tweeter speaker. However taking actual dome light out, there is no power to that wiring.

To the best of my knowledge the dome lights, hazard lights and power mirrors are all on the same circuit, well the hazard lights still work :huh:. This circuit (if I read the wiring diagram correctly) is on fuse 56, which I checked and it isn't blown.

This leads me to believe that there isn't a bad ground as the other items on the circuit work, and the fuse isn't blown. So now I am thinking there is a chaffed wire or a cut wire somewhere, which I haven't ripped the dash any further apart to investigate/find

Next step is to have someone with a tech II check the BCM to make sure the right voltage is being supplied to the circuit.

If anyone has any ideas as to what the solution may be, they would be greatly appreciated.
 
cgalpha08

cgalpha08

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So I did some more digging on the wiring diagrams and have come to this conclusion. I think the BCM needs a slight reprogram to supply the righ voltage to the circuit. If you look in the diagrams below line 1732 (orange) supplies the "hot" power to the dome lights, outside power mirrors, foot well lights, and vanity mirror lights. This line, comes from the BCM. I think this is the logical next step. Thoughts?

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JPaul

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Way up north, UT
I'd be very surprised if it's a programming issue with the BCM, programs don't just change on their own generally speaking, and I don't know why it would've been reprogrammed.

Have you checked to see if there is voltage coming from A29 and A20 pins on the BCM connector? If there isn't then I would suspect the BCM has been damaged due to a short somewhere (which would suck since that means it could happen again, there might still be a shorted wire somewhere).

If there is voltage then it's a cut wire. If there isn't then it might still just be a damaged wire (I'd imagine the BCM has some kind of short circuit protection inside it since there aren't any fuses after it to protect it and the wiring from shorts) and you'd want to pull the connector off the BCM and test between the pins and ground with an ohm meter to check for a short. I'd disconnect the power window switch and pull the bulbs out of the lights when testing. With that all unhooked it should be an open circuit (infinity ohms). Any kind of resistance reading otherwise will indicate a shorted wire.
 
cgalpha08

cgalpha08

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JPaul said:
I'd be very surprised if it's a programming issue with the BCM, programs don't just change on their own generally speaking, and I don't know why it would've been reprogrammed.

Have you checked to see if there is voltage coming from A29 and A20 pins on the BCM connector? If there isn't then I would suspect the BCM has been damaged due to a short somewhere (which would suck since that means it could happen again, there might still be a shorted wire somewhere).

If there is voltage then it's a cut wire. If there isn't then it might still just be a damaged wire (I'd imagine the BCM has some kind of short circuit protection inside it since there aren't any fuses after it to protect it and the wiring from shorts) and you'd want to pull the connector off the BCM and test between the pins and ground with an ohm meter to check for a short. I'd disconnect the power window switch and pull the bulbs out of the lights when testing. With that all unhooked it should be an open circuit (infinity ohms). Any kind of resistance reading otherwise will indicate a shorted wire.
Click to expand...

No I haven't checked those pins yet. Hmm ok ill have to get a more sophisticated electrical tester to do that with the BCM. Did you mean A29 and A30? I think A20 is for the wiper mechanism, which does work as its supposed to.

The reason I suggested a programming issue is because one of the troubleshooting steps in the service manual is to make sure there is adequate voltage supply coming from the BCM, which I am assuming you either need a more advanced voltmeter than I have or a tech II of some kind.(I don't know what the actual voltage is supposed to be).

The strange part is that everything else works on the vehicle electronically speaking. So I am not completely sold on the BCM being completely bad...yet lol.
 
4speedfunk

4speedfunk

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Tardville
As always...check the battery connections first. After that, check the main harness snake heads that plug into the bottom of the main fuse block. After that...check the plugs at the BCM (ps kick panel). These are prone to corrosion from blocked sunroof drains.

Look for pins bent over sideways, where someone crammed the plugs onto the connectors. I've seen this on several H3's.
 
cgalpha08

cgalpha08

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4speedfunk said:
As always...check the battery connections first. After that, check the main harness snake heads that plug into the bottom of the main fuse block. After that...check the plugs at the BCM (ps kick panel). These are prone to corrosion from blocked sunroof drains.


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Click to expand...
Checked the battery, little bit of corrosion on the positive side connection. Nothing too serious.

Haven't checked underneath the fuse box, so I will add that to the list along with the BCM.

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cgalpha08

cgalpha08

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Well stupid me killed the battery with all of my poking and prodding into the electrical system, so add that to the list

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cgalpha08

cgalpha08

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Took awhile but finally got an initial diagnosis from my local mechanic, who is recommending I take it to the dealer, because of the proprietary Gm software.
He pulled 3 codes from the BCM

B2552
B1420
B2583

Anyone have any idea what these codes represent?

Before anyone asks/mentions, the sunroof drains do work, and I have not found any evidence of water coming in.
 
cgalpha08

cgalpha08

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So i found this website that has a lot of codes on it
http://www.totalcardiagnostics.com/...ufacturer-obd2-codes-and-their-meanings#other

B1420 is Passenger Power Window Motor Circuit Short To Battery
B2583 is Child Seat Detection Circuit Short to Ground
B2552 isn't listed

Thoughts on what direction to proceed? Is it as simple as having the dealer reflash the BCM? I know outright replacing it is going to cost north of 1G.

EDIT:
Another website has B1420 listed as Seat Switch Input Status, if anyone can decode these for H3 and GM specific, that would be great, it would at least give me a place to start troubleshooting at.
 
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4speedfunk

4speedfunk

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Clearly you have some wrong info somewhere. You need to determine which code description is correct (seat or high beams) (backups or windows) etc. I see several are listed as "shorts" and that makes them easier to find than low voltage or open circuits.

Back-up lights are often effected by a chafed wiring harness near the rear license plate. Check behind the rear bumper where the harness crosses a seam in the body. I run across this all the time when swapping on THORparts bumpers. The body seam slowly carves its way thru the wires...
c0c8f44034748d552256a86e5e2343d1.jpg

I've also heard of another harness chafing issue above the glove box. It can be accessed by removing the center plate if the dash...it will be in the upper right corner.

Amazingly...these shorts rarely pop a fuse. Instead they back-feed voltage into the truck and it can cause all kinds of strange behavior.
 
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A

atvspeed4

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massachusetts
When I bought my alpha I had several check engine, rough idle, lights not working. Ended up being the dealer had to replace large portion of the wiring harness from the fuse block back and also same thing as picture above in back of my alpha. I guess it's more common in the second gen 08+ and rarely come up in the 2006

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cgalpha08

cgalpha08

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I'll check the wires out back.

I'm going to the dealer today for routine maintenance on my Silverado anyway. I'll ask them to tell me what the codes are, hopefully they don't give me a lot of fuss about not having the vehicle there and blah blah

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chaos254

chaos254

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DTC Descriptor
DTC B2582 00


  • Headlamp High Beam Control Circuit Low

Diagnostic Fault Information


152867591


Circuit/System Description

When the body control module (BCM) receives a ground signal from the multifunction high beam or flash to pass (FTP) switch commanding to illuminate the high beam headlamps, the BCM will energize the HI/LO BEAM relay by applying B+ to the HI/LO BEAM relay control circuit.

Conditions for Running the DTC

Battery voltage must be between 9-16 volts.

Conditions for Setting the DTC

B2582

When the BCM receives a high beam switch on command and the front fog lamp relay control circuit is shorted to ground.

B2583

When the BCM receives a high beam switch off command and the front fog lamp relay control circuit is shorted to voltage.

Action Taken When the DTC Sets

The high beam headlamps will not operate or will remain always on.

Conditions for Clearing the DTC


  • This DTC will clear on current status after the condition for setting the fault is corrected.
  • A history DTC will clear after 100 consecutive ignition cycles without a fault present.

Circuit/System Testing

High Beam Relay Control Circuit Test


  1. Ignition OFF, disconnect the HI/LO BEAM relay.
  2. Test for less than 5 ohms between the relay ground terminal and ground.
¤If less than the specified value, test the ground circuit for an open/high resistance.

  1. Connect a test lamp between the relay coil control circuit terminal and the ground circuit terminal.
  2. Ignition ON, operate the high beam switch ON and OFF with a scan tool. The test lamp should turn ON and OFF.
¤If the test lamp is always ON, test the control circuit for a short to voltage. If the circuit tests normal, replace the BCM.
¤If the test lamp is always OFF, test the control circuit for a short to ground or an open/high resistance. If the circuit tests normal, replace the BCM.

  1. If all circuits test normal, test or replace the relay.




DTC B1420


  • Device Voltage Circuit
Diagnostic Fault Information


152866059


Typical Scan Tool Data

152866060


Circuit/System Description

The body control module (BCM) monitors the battery voltage on the battery voltage signal circuit. Damage to components, and incorrect data may occur when the voltage is out of range.

Conditions for Running the DTC

The ignition is ON.

Conditions for Setting the DTC

Battery voltage is outside the range of 9-16 V for 1 second.

Action Taken When the DTC Sets


  • The BCM will disable its outputs when a high voltage condition is detected.
  • The BCM inhibits the setting of other DTCs.
Conditions for Clearing the DTC

The DTC passes when the malfunction is no longer present.

Diagnostic Aids



  • Overcharging with a battery charger and jump starting may set this DTC.
  • A high or low voltage value in multiple modules indicates a concern in the charging system.

Circuit/System Verification



  1. Engine running, accessories OFF, measure and record the voltage at the battery voltage at the battery terminals. The voltage should be between 12.6V and 15.0V.
¤If not within the specified range, refer to Charging System Test (See: Starting and Charging\Testing and Inspection\Component Tests and General Diagnostics).

  1. Observe the scan tool BCM Battery Voltage parameter. The reading should be between 12.6V and 15.0V.
Circuit/System Testing



  1. Ignition OFF, disconnect the harness connectors at the BCM.
  2. Ignition OFF and scan tool disconnected, open and close the driver door, and wait 1 minute. Test for less than 5Ohms between the ground circuit terminal B3 X1 and ground.
¤If greater than the specified range, test the ground circuit for an open/high resistance.

  1. Verify that a test lamp illuminates between the B+ circuit terminals listed below and ground.

    • Terminal A7 X1
    • Terminal B5 X1
    • Terminal B8 X1
¤If the test lamp does not illuminate, test the B+ circuit for a short to ground or an open/high resistance.

  1. If all circuits test normal, replace the BCM.
 
cgalpha08

cgalpha08

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Dealer will have to get back with me on the codes, manager was busy.

According to AutoZone the battery is bad, not enough cold crank amps, but it's reading 12.99 volts with the car off.

Is it possible a new battery will fix my issues?

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chaos254

chaos254

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Battery replacement should be first since low voltage can cause a lot of issues. Retest for codes after you replace the battery and see if they come back

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cgalpha08

cgalpha08

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chaos254 said:
Battery replacement should be first since low voltage can cause a lot of issues. Retest for codes after you replace the battery and see if they come back

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Click to expand...
Isn't 12.99 in the range of correct voltage that the battery should be producing?

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chaos254

chaos254

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It is but under a load the voltage can drop significantly. Battery testers will load test the battery to determine if it passes or fails.

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cgalpha08

cgalpha08

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chaos254 said:
It is but under a load the voltage can drop significantly. Battery testers will load test the battery to determine if it passes or fails.

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Click to expand...
I gotcha. I may swap in my truck battery real quick and see what happens, highly doubt AutoZone will let me just take a battery off the shelf and throw it in to test a theory lol

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cgalpha08

cgalpha08

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Chaos, got another question for ya.

Would under load mean, when the engine is running and/or when just the rest of the electronics are on without the engine on?

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Mr_Rich

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cgalpha08 said:
Dealer will have to get back with me on the codes, manager was busy.

According to AutoZone the battery is bad, not enough cold crank amps, but it's reading 12.99 volts with the car off.

Is it possible a new battery will fix my issues?

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Click to expand...

I wouldn't rely on Autozone under these circumstances. 12.99 volts is more than enough; almost too much. My battery is 12.2 volts with switch off; more than enough. What you want to pay attention to is the voltage drop on starting; no less than 9 volts for that brief starting period. When your truck engine is running turn on all your accessories like radio, AC, lights, etc. and measure the voltage. Make sure that you have more than 12.2 V under these conditions to make sure your alt. is charging the battery.
 
cgalpha08

cgalpha08

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Mr_Rich said:
I wouldn't rely on Autozone under these circumstances. 12.99 volts is more than enough; almost too much. My battery is 12.2 volts with switch off; more than enough. What you want to pay attention to is the voltage drop on starting; no less than 9 volts for that brief starting period. When your truck engine is running turn on all your accessories like radio, AC, lights, etc. and measure the voltage. Make sure that you have more than 12.2 V under these conditions to make sure your alt. is charging the battery.
Click to expand...
Well tested as you suggested. Was getting around 12.8-12.6v with the engine off. Read 9v during that brief startup period then back to upper 14v with the engine on, radio on. It would fluctuate some between upper 14v to lower 14v, even as low as upper 13v, assuming that's the alternator working.

This points me back towards the BCM as the likely issue. Seems as if the system has more than enough voltage running through it. Looks like I'll need to tear into that next unless anyone has any other ideas.

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