Owners of 2014-2015 Jeep Cherokee vehicles may describe a drone noise at steady state engine RPM. The drone noise may sound similar to a louder-than-normal engine exhaust noise. 

Unless you have just started in the automotive field in the last few weeks, you likely have faced this work order. A customer is concerned about exhaust noise. You get in the vehicle and start the road test. The exhaust is quiet, but the familiar hum or growl of a wheel bearing is oh so familiar.

During my five plus decades of being in the automotive service and repair industry I have learned that diagnosing an engine performance problem, drivability problem or electrical problem is not an exact science. I have always favored symptom-based diagnostics, where once we have identified the symptom we focus our testing on a specific area

High voltage (HV) is isolated from the chassis for good reasons. When any high voltage part has a connection to the chassis, that could spell trouble, depending on how much current the connection can carry. The engineers have cleverly designed circuits and strategies that can determine a “lack of isolation” and report that to your scan tool and set a warning light. How does that detection system work?

Performing diagnostics is something many of us do each day, without much thought, but most seasoned technicians have a detailed diagnostic approach that they employ. They have an action plan — a diagnostic checklist — that they follow from start to finish with remarkable success.

We're covering engine oil filters for gasoline-fueled engines, along with cabin air filters.

This article will compare the low voltage system to the high voltage system and explain how a 12-volt brain can get confused. It is essential that you master the principles of electronic controls, reprogramming, oscilloscope usage, reading wiring diagrams and all aspects of electronic systems used in today’s modern vehicles in order to transition into high voltage systems.

All technicians are aware that the scan tool holds the No. 1 priority in our initial diagnostic strategies. In my personal experience, the No. 2 tool in diagnostics is the DVOM, known as the digital volt-ohm meter or multimeter. In the event of an electrical problem, the DVOM is the essential tool.

While the installation of the correct engine oil may not be an important item to a customer when they arrive at our shop for service, the type of oil that is installed in the engine is beyond important. As technicians it is our job to ensure that the correct engine oil is installed that will meet or exceed what the manufacturer expects.

Check the bleeder valve. If you suspect a bad caliper, it may be an issue with sticky/seized piston(s), but don’t jump to that conclusion right off the bat.

If the MIL is on with DTC P2798 on a 2017 Chevy Bolt EV vehicles, the cause may be damaged wire insulation resulting in a short to ground or corrosion in the line to the G5 transmission fluid pump harness.

Some 2017-2019 Toyota Tacoma trucks equipped with the BD20 differential (non-TRD) may exhibit a noise or vibration from the rear at low speeds or while braking. This may be caused by excessive clearance between the brake drum and axle drum flange.

This bulletin applies to 2004-2009 and 2010-2015 Toyota 4Runner vehicles equipped with part time 4WD. A cyclical groaning/grinding noise may be heard at the front differential when in 2WD that goes away when placed in 4WD.

Some 2017 Ford F-150 trucks equipped with a 3.5L GTDI engine may exhibit a MIL on with DTC P164C (internal control module start-stop performance) stored in the PCM. 

Some 2011-2012 Ford F-Super Duty vehicles equipped with a 6.7L diesel engine built on or before Feb. 12, 2012, may exhibit a run-rough and/or misfire concern with or without DTCs P0300, P0301, P0302, P0303, P0304, P0305, P0306, P0307 and P0308.

The park assist feature of some 2009 GM models — including Buicks, Cadillacs, Chevys, GMCs and the Saturn Outlook  — may not be operative, and the vehicles may be showing messages that indicate a problem.

2014-2015 Ram Pro Master vehicles are equipped with a spare tire winch. The customer may complain about a squeak noise at the rear, and/or being unable to lower or raise the spare tire/wheel.

Some 2011-2016 Ford F-Super Duty trucks equipped with a 6.7L diesel engine may exhibit a fuel knock noise at idle, an illuminated MIL and one or more of nearly two dozen DTCs.

Some customers driving a 2015-2018 Chevy Silverado may comment on a surging condition that is felt when driving. During diagnosis, the technician may determine this as a torque converter shudder. This condition may be caused by additives in the transmission fluid that may have depleted during vehicle operation. Some of these additives assist with regulating a consistent slip rate of the clutches.

This bulletin applies to 2014-2016 Jeep Cherokee vehicles equipped with a 2.4L I4 Multiair engine and built on or before July 26, 2016. The customer may describe a slight engine compartment noise. This may be at the purge control valve area.

The spark plug has a straightforward job to do. It’s responsible for igniting the air/fuel mixture in the engine’s combustion chamber initiating the power stroke. But this task is far from simple. The spark plug’s operating environment is extreme with combustion temperatures reaching 1500 F and peak cylinder pressure reaching 1,000 psi or more.

Certain 2015 Cadillac Escalade and Escalade ESV vehicles equipped with a 6.2L engine and 8-speed automatic transmission may have a condition in which the U-joint retainer bolts lose index.

This bulletin applies to 2014-2019 Chevrolet Corvette and 2016-2019 Camaro vehicles equipped with a 6.2L LT1/LT4 engine. You may find a DTC P06DD set in addition to no or low oil pressure.

A small internal brake fluid leak inside the brake booster assembly may be causing the brake, ABS and/or TRAC warning lights to illuminate on some 2011-2015 Toyota Prius and 2012-2015 Prius Plug-in Hybrid vehicles.

Some 2015 Ford Escape vehicles built on Oct. 1, 2014, through Nov. 30, 2014, may exhibit a no-crank condition along with other inoperative electrical systems. Check the 12-volt battery for loose, damaged or corroded connections. Check battery state of charge.