Tech Tip: GM Vehicle has DTC P0757 Set, MIL Illuminated and Slipping Transmission
Some customers may comment on any of the following conditions – an illuminated MIL (where DTC P0757 is found as a history code), no third and fourth gear and the the transmission does not shift correctly.
Tech Tip: DTC P0756 Diagnostic Tips on GM, Hummer and Saab Vehicles
Some technicians may have difficulty diagnosing DTC P0756, 2-3 Shift Valve Performance on 4L60-E, 4L65-E or 4L70E automatic transmissions. As detailed in the service manual, when the PCM detects a 4-3-3-4 shift pattern, DTC P0756 will set. Some customers may also describe a condition of a second, third or fourth gear start that may have the same causes but has not set this DTC yet.
TECH TIP: GM Transmissions/Transfer Case: Slight Vehicle Movement in Park at Start Up
Some vehicles may rock or move slightly forward or rearward while in park at start up after cold soak. This condition may be accompanied by a clunk noise. This is a slight movement that is more often seen visually, rather than felt, when viewed from the outside and using the auto-start feature, if equipped.
Tech Tip: GM’s A/T is Stuck in 2nd/3rd Gear
Some customers may comment on one or more of the following conditions: the MIL is on; the transmission is defaulted to second gear (4L80/85-E); the transmission is defaulted to third gear (4L60/65-E); the instrument cluster is inoperative.
Tech Tip: GM Liquid Gasket/Engine Sealants Information
In 2005, General Motors consolidated the use of all liquid gaskets/engine sealants. At that time, two sealants replaced all previous sealants referred to in service information and/or the service manual.
Tech Tip: Front Passenger Seat Accessory Precautions
Post-collision repair requirements differ from manufacturer to manufacturer. Thus, you must be prepared to evaluate, research and document each and every crash-damaged vehicle that’s brought into your repair facility. Seat belts, steering systems, occupant sensors, on-board diagnostics and air bag components and systems, as well as proper alignment of structurally related components, are only a few of the critical considerations confronting you ….
Tech Tip: Sludgy Saab May Rattle Your Chain
If a Saab owner complains about a rattling timing chain, oil sludge or any of the other conditions described in this Tech Tip, follow the recommended procedures. Various conditions can cause the formation of oil sludge in the engine or a rattling noise from the timing chain and balancer shaft chain. Additional symptoms may include abnormal whining, bellowing or knocking noise from the engine and/or an illuminated oil pressure lamp ….
GM Tech Tip: Inspect and Ensure the Integrity of Wiring Harness Connectors
The first step in any type of electrical diagnosis is a visual and physical inspection of the wiring harness connectors for integrity. Many times, the vehicle may be repaired just by disconnecting and reconnecting the connectors. As with all repairs to wiring harness connectors and terminals, a pull test of the terminals within the connector should be performed. A pull test is performed by ….
Tech Tip: Choosing the Right Coolant
What makes choosing the right coolant so confusing today is that the automakers themselves can’t agree on what type of coolant chemistry is best for their vehicles. Some vehicle manufacturers prefer one type of corrosion inhibitors in their coolants, while other vehicle manufacturers may insist on a different type ….
Tech Tip: Tool Needed to Replace Timing Chain-Driven Water Pump
Replacing this water pump requires a special tool to secure the water pump sprocket. Failure to do so could result in misalignment of the engine’s balance shafts or significant engine damage. Remove the water pump access plate from the timing cover and install J 43651 Water Pump Sprocket Holding Tool, or equivalent. Secure tool to the sprocket and front cover and remove the sprocket bolts. Remove the water ….
Saab Tech Tip: Reduced Performance and DTC for EGR Valve
Under certain driving conditions, such as a lot of city driving, increased carbon deposits may cause the EGR valve to seize or jam in the open position. This can result in reduced performance for the car as the boost pressure leaks out via the EGR valve. In some cases, DTCs P0400, P0401 and P0402 may be generated ….
Tech Tip: Locating the Source of an Engine Leak
Nothing upsets pernickety homeowners more than driveway stains caused by oil leaking from the vehicles of visiting friends and family. However, many of the vehicles that suffer oil leaks can be cured. It just takes a bit of detective work to locate the leak source and some labor time to make the repair. In essence, those technicians who take on leaking engine work aren’t only providing environmental repairs to the vehicle, they’re repairing relationships among family members and ….