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. 

Squeak Noise from Rear of Vehicle

1999-2007 Chevrolet Silverado (Classic), GMC Sierra (Classic); 2007-2009 Chevrolet Colorado, Chevrolet Silverado, GMC Canyon, GMC Sierra, HUMMER H3, HUMMER H3T 

A squeak noise may be coming from the rear of the vehicle. During normal operation, certain vehicles may exhibit a squeaking noise that may be traced to the rear leaf springs. While this noise is an operating characteristic of leaf springs, the roads that the vehicle is driven on will affect the frequency and severity of this noise. 

This condition may be due to debris getting between the leaf springs. It has been found that the application of grease to the rear leaf springs will correct this condition and do a better job of preventing the noise from reoccurring than replacement of the springs. 

To grease the springs, pressure wash the springs to remove as much dirt and debris as possible and dry the springs with compressed air. 

Apply a liberal amount of grease under the front and rear tip inserts for the #2 and #3 leaves, on top of the tip inserts, and in between the #1 and #2, and #2 and #3 leaves. 

Periodic cleanings and grease re-application may be necessary throughout the life of the vehicle. 

If this procedure does not correct the noise on 1500 Series (1/2 ton) models built prior to October 2004, the noise may be caused by an incorrectly dimensioned splay clip (the band holding the ends of the leafs together) that interferes with the leaf springs. A 5 mm (0.197 in) wider splay clip was introduced early in the 2005 model year to provide additional clearance. To correct this condition, it may be necessary to replace the rear leaf spring assembly. There was no change to the part number. 

For more information, refer to GM bulletin # 06-03-09-004B. 

OnStar^® Power Consumption 

2000-2010 OnStar-equipped Vehicles with Digital Hardware 

During battery parasitic drain testing, it is important to understand the power cycles of the various OnStar systems in order to avoid confusion about normal power consumption readings. 

All OnStar customers with currently active vehicles have digital/analog cellular capability. A green status LED on the OnStar keypad normally indicates an active OnStar account. (Fig. 13) A red LED indicates a system DTC. On Gen 6 and later systems, a clear or "dark" LED may indicate the OnStar system has been deactivated or may possibly have a no power concern/no communication.

 

The OnStar system will stay powered up after the ignition is off for an extended time in order to allow for remote services like door unlock, horn chirp, light flash, etc., to take place as requested by the driver. Power cycle times vary depending on the generation of the OnStar system, and may be powered up continuously from 48 hours to 120 hours after the ignition is off. Technicians may identify the system generation by using a scan tool or by using www.onstarenrollment.com. 

The expected current draw of the OnStar module is:

IGN ON - 240 to 400 mA

IGN OFF - 3 to 20 mA for 48 hours

IGN OFF - after 48 hours (120 hours on specified VCPs) - 0.2 to 0.8 mA  

Fluid Flushing Requirements 

2005-2010 Chrysler, Dodge and Jeep vehicles 

Chrysler Group vehicle fluid systems do not require regular flushing. These systems include: engine oil, transmission oil, axle lube, brake fluid, power steering fluid, and refrigerant. The only exception to this requirement are those fluid changes that are published in the vehicle maintenance schedules, e.g. engine coolant, and in instances where a failure has occurred and/or the system has become compromised, contaminated or overheated beyond the normal operating range. 

Aftermarket chemicals to flush the engine, transmission, brake or steering systems are not recommended. Chemicals contained in these products can damage the system elastomeric components, and contaminate the component fluid, leading to loss of system/component durability and service life. When necessary, only the original approved system fluid should be used to flush these components using approved equipment. 

If the engine coolant contains a considerable amount of sediment, clean and flush the system, followed by a thorough rinsing to remove all deposits and chemicals. Refill with a minimum of a 50% mixture of the specified coolant and distilled water. 

Refer to Chrysler bulletin #26-001-09 for more information.