Here's some information about the fuses and some other components now in use within the BEC (Bused Electrical Center) (fig. 1) of various GM vehicle platforms. But first, some background.

The purpose of circuit protection is to protect the wiring during normal and overload conditions. An overload could be caused by a short circuit, pinched wire or a component failure.

There are two kinds of short circuits:

A direct short is caused by excessive current flow. For instance, 200% of the fuse rating, resulting in quick fuse failure.

A resistive short is caused by a gradual overload and heating of the fuse until it fails. For instance, 135% of the fuse rating.

Remember, the circuit protection device is applied to protect only the wiring and not the electrical load in the circuit.

A fuse is a temperature-sensitive device. This means that changes in ambient temperature will change or re-rate the fuse. Fuse ratings are based on an ambient temperature of 25°C (77°F).

Example: a 10A fuse at 25°C (77°F) would re-rate to 9A at 105°C (221°F). The same fuse would open in 50 seconds at 25°C (77°F) but only 30 seconds at 105°C (221°F).

TYPES OF CIRCUIT PROTECTION

Years ago the glass fuse (fig. 2) had a calibrated wire that would burn open if a certain amperage threshold was exceeded for a specific amount of time.

The next fuse type we are most familiar with is the Autofuse (ATO) fuse (fig. 3). This fuse was introduced in 1969.

The next fuse type to make its appearance was the Mini-Fuse (fig. 4). This fuse was introduced in 1985.

At about the same time, the Maxi-Fuse was also introduced (fig. 5). It was designed to take the place of the fuse-link.

A close cousin of the Maxi-Fuse is the new J-Case fuse (fig. 6). This fuse was introduced in about 2000.

In 2005 the new low profile Micro fuse was introduced (fig. 7). Its terminals are placed alongside the fuse so it has a much lower height when installed. All this is an effort to get more "stuff" into a smaller and lighter BEC as vehicles get smaller but with more electronic capabilities.

There is also a low profile J-Case fuse (fig. 8).

CIRCUIT BREAKERS

The circuit breaker has also gone through some changes over the years. There are two kinds of circuit breakers in use in GM vehicles today, cycling and non-cycling.

Cycling Circuit Breaker

The function of a circuit breaker is to open the circuit once a certain amperage threshold is exceeded for a specific amount of time. When the circuit breaker cools, it closes again.

A cycling circuit breaker (fig. 9) will automatically reset after a certain period of time.

- If the overload is still present, the cycling circuit breaker reopens and starts the cycle again. Cycling breakers are used primarily for headlamp lighting circuits.

- If the high current condition is gone, the cycling circuit breaker stays closed and the vehicle function is restored.

The typical cycling circuit breaker plugs into its terminals in a manner similar to a fuse.

Non-cycling Circuit Breaker

A non-cycling circuit breaker (fig. 10) opens the overloaded circuit similar to the operation of a cycling circuit breaker.

However, the non-cycling type resets only after:

- the overload condition is removed

- and no current flow is present.

Diodes

Although diodes (fig. 11) are not circuit protection in the same sense as fuses and circuit breakers, they are included here because you may also see them plugged into a BEC along with fuses, circuit breakers and relays.

Diodes are used as one-way electrical valves. The main purpose is to prevent high voltage from a device from returning through a circuit and damaging another component.

Diodes can also be used to prevent voltage feedback within some series parallel control circuits.

Because diodes are one-way devices, they must be installed in the correct orientation.
A symbol on the top indicates the direction of current flow.

- Thanks to John Roberts

Some confusion has resulted when a technician pulls one of the new Micro fuses for the first time. Because the terminals are alongside the body of the fuse, and don't protrude as they do on Minis and Maxis, the first thought is that the terminals have broken off and remained in the BEC (fig. 12). As explained elsewhere, the Micros are made this way so they have  a much lower height when installed. This permits using a smaller and lighter BEC.

Some third party applications may cause communication problems when using the Pass-Thru programming method. The list below includes known offenders; there may be others.

Most of these applications use some type of port blocking or filtering function, or they will recognize Java as an intruder and will not allow the SPS client to open.

Problems may also be caused by any security suite that contains a personal firewall component, as well as add-on tool bars that have an imbedded pop up blocker.

- Symantec PC Anywhere

- Symantec Anti Virus Corporate version (may require additional configuration)

- Symantec Internet Security Suite (contains a personal firewall)

- Symantec Personal Firewall (standalone)

- McAfee Security Suite (contains a personal firewall)

- McAfee Personal Firewall (standalone)

- Add Aware

- Spybot

- HiJack This

- Google Tool Bar

- Yahoo Tool Bar

- AOL Tool Bar

- AVG Free Anti Virus (if improperly configured)

You should have Microsoft XP Professional installed as your operating system and Microsoft Internet Explorer 6 or 7 as your internet browser. These programs have an imbedded personal firewall and popup blockers. So, third party options are not necessary and may create unexpected problems.

These third party security applications must be properly uninstalled through the Add/Remove Programs function of the Windows Control panel. If you have questions or need guidance in configuring or removing these applications, contact your IT support person or IT support vendor.

TIP: If notification appears on your computer's toolbar to accept automatic updates, do not accept them. Doing so may cause features to be installed on your computer that will cause communication problems. Some of the updates to avoid include Google Toolbar, Yahoo Toolbar, Adobe Acrobat and Java.

- Thanks to Jim Young

TIP: This replaces information in the February 2007 TechLink.

On the 2007 Chevrolet Equinox and Pontiac Torrent, here’s how to remove the Underhood Electrical Center/Junction Block Cover without damage.

To remove the junction block cover, push in on the two locking tabs located on the rear of the cover and lift (fig. 13).

A Front

B Rear

TIP: No flat bladed tool is required.

To install, fit together the tabs located on the front of the cover and push down on the cover until the tabs on the rear of the cover (closest to dash) click into place.

- Thanks to Alex McKay and Karem Youkhana

Customers may discover that DVDs purchased outside the US likely will not play in vehicles sold in the US. This will help explain why.

Motion picture studios require that a DVD includes a code specific to the geographic region in which it is sold.

Similarly, each DVD player is given a code for the region in which it is sold. (fig. 14).

This is called the DVD Region Code. In most cases, the DVD and/or the storage box contains a symbol (fig. 15) denoting the DVD's region code.

In order for a DVD to play, the DVD's region code must match the player's region code.
This means that a disc bought in one country likely will not play on a player bought in another country.

In some parts of the world, a certain tuner calibration may overlap several DVD regions. Each combination is unique.

Recently, for some applications, the DVD region code has been included with SPS programming along with software and calibrations.

It is critical to select the correct calibration when programming a radio.

For each radio receiver, the number of times the DVD region code can be changed is limited; then the radio locks up and cannot be programmed again. Failure to select the proper software/calibration set can lead to a loss of system functionality and cause unnecessary radio replacement.

TIP: Other options that vary with vehicle content include rear camera and amplifier usage.

IMPORTANT: After you have selected a calibration, carefully check the description to ensure that the DVD region code and tuner region are correct.

- Thanks to Steve Falko and Katul Patel

This information applies to 2007 Pontiac G6, Saturn Aura and Outlook and GMC Acadia with 6T70 or 6T75 transmission.

The vehicle may have a transaxle fluid leak from the axle/halfshaft seal on either right or left side. Determine where the leak is located.

TIP: Remember that the halfshafts will sling fluid upwards at times. This may make it look like the leak is coming from the side cover or other location.

The parts and repair restictions have been lifted for axle seal repairs. If the leak is from an axle seal, obtain the parts through normal channels. Use special tool number J-44394-A when installing the axle/halfshaft into the new seal.

IMPORTANT: Failure to use seal protector J-44394-A can cause the seal to be cut and create an immediate leak. In cases of slight damage, leaks will occur as mileage accumulates.

- Thanks to Ronald Mitchell

The owner of a 2007 GMC Acadia or 2007 Saturn Outlook may hear a high pitched buzz or whine noise after the engine is shut off. This buzz or whine noise is coming from the solenoids in the transmission. These solenoids will stay active during the TCM shut down, which will last about ten seconds.

DO NOT make any attempts to repair this concern. This is a normal characteristic of this vehicle.

- Thanks to Ron Erman

This information applies to the 2007 Saturn Vue Greenline Hybrid with 2.4L Engine
(VIN Z - RPO LAT) manufactured before December 10, 2006.

On rare occasions, the following cruise control issues may be experienced with no DTCs stored.

When pressing the “-” or “cruise set” switch, the transmission may downshift, causing the desired cruise control speed to overshoot by approximately 5 mph. After this occurs, the vehicle speed will drop to desired/normal set speed.

A “bump” may be felt when driving in hills with the cruise control on. This "bump" occurs as the engine is making the transition from regeneration fuel cut mode on deceleration to an acceleration with gasoline engine and electric assist.

If the SI diagnostics do not isolate a cause for this concern, it is most likely the result of an ECM calibration issue. On December 10, 2006, an updated ECM calibration was released
in TIS version 12.5 to address this concern. The title of this ECM calibration is "enhanced cruise control performance". This calibration, or any that follow, is designed to address this concern. Vehicles manufactured after the listed breakpoint should already contain this updated ECM calibration.

- Thanks to Jamie Parkhurst

Owners of some 2007 Cadillac Escalade, Escalade ESV or Escalade EXT models may comment on roadnoise or windnoise in the area of:

- driver door area.

- passenger door area.

- rear windows

- rear of the vehicle

FRONT

These are highlights. Details are included in bulletin number 07-08-58-001.

Air may be rushing in one of the following areas:

- Mirrors

- Door filler

- Reveal molding clips may not be properly seating into the door frame.

- Seal around the reveal molding may have moved and is not sealing properly.

Outer Door Glass Reveal Molding -- If the foam seal around the reveal molding is out of position (fig. 16), replace the reveal molding. If reusing the reveal molding, discard the clips and use new ones.

Install the outer reveal molding. Start at the front of the door and work back. Use a small pick tool or screwdriver to ensure engagement of the clips to the door frame (fig. 17). The clip has two barbs, one at each side. When installed correctly, you will hear a snap sound.

Mirror -- Remove the upper extension trim panel (mirror extension trim panel). If the mirror foam is missing, install a replacement (fig. 18).

Before installing the mirror, add a piece of foam to the mirror gasket and tape up the hole in the seal where the wire harness passes through.

Install the mirror. Push up and rotate toward the A pillar to ensure a tight seal.

REAR

These are highlights. Details are included in bulletin number 06-08-66-015B.

Air may be rushing in one of the following areas:

- Rear window reveal molding clips may not be properly seated into the door frame.

- Rear window reveal molding seals may be distorted.

- Rear door frame retaining holes may contain castings or flashings or not be uniform.

Rear Window Reveal Molding -- DO NOT push or force the rear window reveal molding back into place. This may cause the reveal molding to break. Inspect the fit of the rear window reveal moldings to the door frame with a plastic trim stick (fig. 19).

TIP: If no gaps are found between the reveal moldings and door frame, refer to Interior or Exterior Windnoise in SI for further diagnosis.

If gaps are found (fig. 20), remove the reveal molding following SI procedures. If any of the seals are damaged or distorted, replace the rear window reveal molding.

Inspect the door frame retaining holes (fig. 21) for a uniform fit and modify the hole with a small file. Remove any castings or flashings in the door frame retaining holes.

IMPORTANT: Apply GM Synthetic Lubrication with Teflon, p/n 12371287 (In Canada, 10953437), to any bare metal edges.

If reusing the original reveal molding, replace all nine black clips on the window reveal molding with p/n 15286991. The three gold clips are reusable, but replace any damaged or missing clips with p/n 15286992.

Use a hook-style tool or screwdriver to ensure engagement of the clips to the door frame. The clip has two barbs, one at each side. When installed correctly, you will hear a snap sound.

- Thanks to Saundra Massengille

A new essential tool, Sealant Dispenser GE-48326 (fig. 22), has recently been shipped to all GM dealers. Here’s background regarding its use.

In 2005, GM consolidated the use of liquid gaskets/engine sealants (April 2005 TechLink).
At that time, two sealants replaced all previous sealants referred to in SI.

One of these, Engine Sealant 12378521 (p/n 88901148 ACDelco Canada), was released in a 150 gram cartridge, to be used in a conventional caulking gun.

The cartridge and conventional caulking gun proved to be too large and cumbersome in certain instances when used in on-vehicle service.

To address this concern, GM Powertrain Engineering suggested releasing the engine sealant in a 75 gram squeeze tube (fig. 23). This product will be available, packaged six to the carton, with nozzle.

The GM Powertrain specification for applying this sealant is an even bead, 3 mm (0.118 in.) diameter. Due to the high viscosity of the sealant, a dispenser is required to meet this specification.

The GE-48326 Sealant Dispenser provides the ability to apply the sealant to specification using one hand, even in areas not accessible using the p/n 12378521 (Canada p/n 88901148) Engine Sealant cartridge and caulking gun.

- Thanks to Joe Sraj

On the 2007 Acadia and Outlook with Navigation radio UZR, if the navigation disc is inserted into the CD slot on the face of the navigation radio, it may not eject. The correct location for the navigation DVD is located behind the radio face plate.

To eject the disc from the radio, follow these steps.

1. Turn the ignition key off.

2. Open the driver door for one minute.

3. Press the Eject button twice and wait for disc to be ejected.

TIP: This procedure also applies to any other disc types that are not ejectable with the radio on. (DVD videos, MP3 discs, CDs)

- Thanks to Ron Erman

The owners of some full-size 2007 pickups may comment that their power rear slider
( RPO A48 ) will not close. This may be due to the pull side cable ball end becoming separated from the lower side of the sliding window.

It is not necessary to replace the entire rear window slider assembly. Replace the window regulator p/n 25782000. Refer to SI document 1855244 for details.

- Thanks to Steve Love

This information applies to the 2006-07 Chevrolet Impala and Monte Carlo with Remote Keyless Entry (RKE).

Originally, the Remote Control Door Lock Receiver (RCDLR) used the antenna in the front windshield as well as the coax antenna for reception from the RKE fobs and Tire Pressure Monitor (TPM) sensors.

When the vehicle was driven down the road, static electricity could build up and discharge (electrostatic discharge), which could damage the RCDLR. This could cause the signal reception range to drop to 20 ft (6 m) instead of the designed 250 ft (76 m).

TIP: A Service Tire Monitor System message may be displayed.

When replacing the RCDLR for this condition, install a new coax antenna (fig. 24) according to the following information.

TIP: For more information, see bulletin 06-08-52-002D.

TIP: SI is being revised to include the new procedure.

OVERVIEW

The updated coax antenna has been designed so there is no longer a need to use an antenna in the windshield. The updated coax antenna is packaged completely within the
A-pillar.

By design, the new coax antenna does not attach to the windshield. The old antenna will remain in the windshield but will be non-functional. Current production vehicles are being built without the antenna in the windshield.

Impala, Monte Carlo -- Route the new coax cable from the RCDLR across the IP toward the A-pillar. The ground ring terminal is moved to the IP carrier bolt from the pillar (fig. 25). Install the retainers on the coax antenna into the existing holes in the A-pillar, making sure the exposed core of the coax antenna does not touch the A-pillar.

Part Numbers

The part number of the new coax antenna is 25837954 for Impala and 25845987 for Monte Carlo.

- Thanks to John M. Buglione and Dennis Kosmowski

Here are some tips on the Passenger Sensing System on these vehicles:

- Grand Prix
- LaCrosse/Allure
- Malibu
- G6

- Aura
- Vue
- Ion

How the System Works

The main function of the Passenger Sensing System (PSS) is to determine whether to turn the right front passenger airbag ON or OFF, based on the occupant's size and weight.

For additional information, a streaming video from the GM Training website is available. Click Web Video Library from the main menu, then Technical, then do a key word search on Occupant. The course, 22048.40V - Occupant Safety Systems, will be at the top of the list. You can also call 1.800.393.4831 to order a copy of this video.

Flashing Codes and Re-zeroing Process

The diagnostic trouble code (DTC) information for the Passenger Sensing System (PSS) can be retrieved with the Tech 2 tool and displayed through the passenger airbag status display (fig. 26).

This system displays only B0081 or B0092 on the Tech 2. To access detailed diagnostic codes, follow the SI instructions for flashing DTCs.

The Tech 2 command sequence takes a total of 10 seconds to transmit, during which the status display will change its illumination intensity level according to the pattern defined for that sequence.

If the PSS receives the command successfully, it will command both telltales to full illumination for 1 second, then turn them off for another second.

Then it will display the most significant digit of the DTC by commanding the OFF telltale to flash for a number of times representing the digit.

After the most significant digit has been displayed, the system will display the least significant digit by flashing the ON telltale.

For example, DTC 36 will flash the ON telltale 3 times, then the OFF telltale 6 times.

If the DTC is active (the condition that created the fault is still present), the code will be displayed two consecutive times.

If the DTC is a history code (the fault condition is no longer present), the code will be displayed only once.

The system will display all active codes first, then the history codes.

The DTCs are defined as follows:

Generally, if the PSS has history codes only and no active codes are currently set, there is no need to replace the system. The history codes still need to be cleared through the Tech 2 tool, and appropriate electrical tests and visual inspections must be conducted in order to ensure that there is no intermittent problem.

After installing a PSS service kit, the system needs to be re-zeroed using the Tech 2 tool. This will update the empty seat reference values stored in the ECU and ensure proper system performance.

TIP: As a preventive measure that enforces re-zeroing after its installation, the service kit comes with an active DTC set. If the codes are checked before the system is re-zeroed, a DTC56 will be displayed. This code will stay active until the system is re-zeroed successfully.

After the PSS recognizes the re-zeroing command, there are two scenarios:

1. If the system classifies the current seat condition as Empty, it will update the reference values and illuminate both airbag status telltales for a period of 10 sec.

2. If the system detects that the seat is not empty or a DTC condition exists, it will command both telltales to alternatively illuminate from off to full illumination in 1 second intervals for a duration of 5 seconds.

In addition, a DTC 32 will set to indicate that the re-zeroing process has failed.

IMPORTANT:

1. If the system fails to re-zero, resend the zero command and follow the instruction above at least three times.

2. During the re-zeroing process, the seat must be empty of any objects and the clearance specified in the service manual must be observed.

Wet Seat

The PSS diagnostic algorithm includes continuously monitoring for a wet seat condition.

A fluid spill on the seat, in particular if the amount is greater than 200 ml, can affect performance and the system may not be able to correctly classify the passenger. For this reason, the PSS sets a DTC34 and defaults to airbag suppress classification.

TIP: Depending on the fluid amount and its distribution after it penetrates the seat cushion, the system may also set a DTC56.

If these codes (34 and 56) are set, the seat cushion assembly must be removed and allowed to air-dry for about 48 hours. After this period the cushion has to be re-installed again and the DTCs checked.

If no active DTCs are present, the history DTCs must be cleared and the system re-zeroed. In this case, no replacement is necessary.

If there are still active codes after the seat is dry, the PSS cushion and module assembly must be replaced.

IMPORTANT: Replace the parts as a set. Cushion and module must not be separated, because they were calibrated as a pair.

- Thanks to Esther Anderson