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mjr15197

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  1. I had the hard shift in the morning but otherwise had no complaints until last night. I was lucky to be able to drive it back to the dealer. It started downshifting hard on its own and stayed in about 2nd gear. It threw codes P0700, P0717, P0776, P0796. '21 Silverado 2.7. 21k miles.
  2. Just let your truck idle for 20 seconds before driving away: Subject:Diagnostic Information on Headlamps Flicker or Momentarily Dim While Driving #05-08-42-001 - (03/07/2005) Models:2004-2005 Buick Rainier 2002-2005 Chevrolet TrailBlazer 2002-2005 GMC Envoy 2003-2004 Oldsmobile Bravada with 4.2L Engine (VIN S -- RPO LL8) A concern regarding headlamps flicker or become dim while driving may be easily mis-diagnosed. It is very important to capture as much information from the customer as possible. Below is a guideline to assist with diagnostics. Verify the customers specific concern. • What time of day does this occur (is it light or dark outside) ? • What driving conditions (vehicle speed, engine speed, throttle position, etc...)? • What was the outside ambient temperature when the condition occurred? • What accessories was the driver using when this condition occurred (A/C, heated seats, rear defogger, etc...)? • If the concern is at dusk, could it be the automatic headlamps changing from DRL to Headlamp mode and possibly back to DRL again? • Are there any other relevant operating conditions? Diagnostic Information • Service Bulletin - 02-06-03-008A - Info - Low Voltage Display on IP Gauge, Lights Dim at Stop Lights, Battery Discharged, No Start, Slow Cranking, Dim Lights at Idle, Low Generator Output (SI Document ID #1540541) • Service Bulletin - 02-06-03-006B - No Start, No Crank, Battery, Batteries, Generator, Gages, SES, SIR, Brake, Security, Theft, ABS, Hot, DIC Messages, Lamp, Light, Battery and Generator Diagnostic Testing and Cadillac Roadside Service (SI Document ID #1563904) • Service Information - Exterior Lighting Systems Description and Operation (SI Document ID #826321) • Service Information - Battery Inspection/Test (Non-HP2) (SI Document ID #653410) • Service Information - Charging System Test (SI Document ID #1468059) • Service Information - Inspect for aftermarket devices that could affect the operation of the system. Refer to Checking Aftermarket Accessories in Wiring Systems (SI Document ID #816776) Important: • Keep in mind high current draw items may cause a noticeable dimming of lights and a fluctuation in the voltmeter may be noted and is a normal operating characteristic of the vehicle. • For 2004-2005 TrailBlazer, Envoy, Rainier and Bravada with the LL8 4.2L engine only, the Secondary Air Injection (AIR) pump activation is thought to be the main contributor to this high current draw condition and is a normal operating characteristic of the vehicle. Refer to Secondary Air Injection System Description (SI Document ID #1298539). For customers whose driving habits tend to run the AIR pump diagnostic test that leads to concerns with the headlight flickering, if the vehicle is allowed to idle for 20 seconds prior to driving, this should allow the passive test to pass and prevent from running the active test that may dim the lights. The passive test should/will usually pass 99 percent of the time, and by allowing the 20 second idle period, it should almost eliminate the active test. Be sure to check for codes and correct related concerns if this condition repeats. Additional high current draw items are rear window defogger, HVAC blower motor, rear air suspension pump along with other components. For easier diagnostics, it may be possible to control or monitor these components with a scan tool. It is important to inspect all related connections, grounds and battery terminals for integrity . A loose or corroded connection may exaggerate the concern, and may cause other symptoms. Refer to Testing for Intermittent Conditions and Poor Connections (SI Document ID #1470165). Corrections/repairs should only be made for specific concerns identified and not related to characteristic of high current draw components.
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