Tech Tips

The following technical tips provide repair information about specific conditions on a variety of vehicles. If you have a tough or unusual service repair, the TSS Technical Assistance Hot Line can help. Call 1-800-825-5886, prompt #2, to speak with a technical expert with the latest OEM information.

 

Service Charging System Message on DIC

 

2005-2009 Chevrolet Corvette; 2004-2009 Cadillac XLR

A Service Charging System message may be displayed on the Driver Information Center (DIC) along with a stored DTC P0621. This condition may be a result of aftermarket spark plugs or an open in circuit number 2540.

Check for aftermarket spark plugs. Plugs that are designed with a "pulse" technology may interfere with this circuit and cause the Service Charging System message in the DIC and/or P0621 DTC to store in the ECM. If aftermarket plugs are installed, replace the plugs with OEM parts.

Also, try the horn to see if it works. If the horn does not work, suspect an open fuse. Circuit 2540 is supplied voltage from the horn fuse, position 2 in the UBEC. This fuse may open if the horn is shorted due to water intrusion.

If the horn is functional, check the integrity of circuit 2540 between the UBEC and the generator. Refer to the appropriate Service Information. Repair circuit 2540 as needed.

 

V Engine Cylinder Bank Naming

 

GM vehicles equipped with a V engine

GM uses two methods of naming cylinder banks in V engines.

For emission related components, cylinder banks are named using a Society of Automotive Engineers (SAE) recommended practice. Bank 1 is the cylinder bank that has the number 1 cylinder, and bank 2 is the cylinder bank that does not have cylinder 1. Cylinder 1 location is given in Service Information category Engine Mechanical.

For other than emission related components, cylinder banks are named Left and Right. This is determined by looking toward the front of the engine from the flywheel end. This method is used whether the engine is installed longitudinally or transversely.

 

Brake Pad Cracks

 

2007-2009 Chevrolet Silverado 3500HD; 2007-2009 GMC Sierra 3500HD -- with brake RPO JK4 or JH7

When performing a brake inspection on a 2007-09 Chevrolet Silverado 3500HD or GMC Sierra 3500HD with brake RPO JK4 or JH7, hairline cracks may be noticed in the pad friction material. (Fig. 16)

Cracks in the friction material can occur after the pads have been subjected to high pad temperatures.

These hairline cracks do not affect the operation of the brake system and the pads should not be replaced if only hairline cracks are found.

 

Battery Charging Precautions

 

1995-2007 Mazda B-Series;1997-2003 Mazda Protégé; 1997-2005 Mazda Miata; 1997-2002 Mazda 626; 1997-2002 Mazda Millenia; 1997-2006 Mazda MPV; 2001-2006 Mazda Tribute; 2003-2007 Mazda6; 2004-2007 Mazda3; 2004-2007 Mazda RX-8; 2006-2007 Mazda5; 2006-2007 Mazda MX-5; 2007 Mazda CX-7

When attempting to re-charge a fully discharged battery, remove it from the vehicle. If a sulphated battery is charged in the vehicle with the battery cables connected and the charger is set to the high charge setting, excessive voltage produced by the charger may result in damage to the Powertrain Control Module, audio system, memory back-up circuits and other electrical devices. Damage may also occur to other electrical components that are activated or that are in use while the battery is being charged in the vehicle.

The maximum voltage for vehicle electrical components is approximately 15 volts. Battery chargers generate at least 15 volts, and in some cases, as much as 20 volts under the high charge setting.

 

Discharged Battery, Slow Starting

 

1997-1998 Buick Skylark; 1997-1998 Chevrolet Cavalier and Malibu; 1997-1998 Oldsmobile Achieva and Cutlass; 1997-1998 Pontiac Grand Am and Sunfire - with 2.2L, 2.4L, 3.1L engines (RPOs LN2, LD9, L82)

The battery may be weak or discharged, the starting motor may turn slowly, or the generator may not be charging.

Check for a loose generator output and battery positive cable terminal at the starting motor. This may cause a high resistance in the battery positive circuit from the generator to the battery. Also inspect the condition of the starting motor B+ stud, wire, ring terminals and nut.

If these conditions are found, the generator and battery should not be damaged and will not require replacement.