Diagnostic Dilemmas: When Over-Voltages Electrocute PCMs
During the past nine months, I’ve had three instances of powertrain control module (PCM) failures on Jeep Wrangler vehicles that were evidently caused by an over-voltage condition. The first case involved an owner who requested that a local shop replace the fuel pump because his 1998 Wrangler was slow-starting in the morning. The shop found the pump pressure was marginal and replaced the pump. Because the Jeep still had the problem, the owner complained about the fuel pump, first to the shop and then to the local jobber supplying the pump.
Diagnostic Solutions: Cylinder Head Repair
Cylinder head gasket failures are one of the most common mechanical issues facing today’s modern import technician. One reason head gasket failures are common is because the cylinder head gasket itself can become a wearing part. Since the aluminum cylinder head expands at a slightly higher rate than the cast-iron cylinder block, the cylinder head actually slides a few thousandths of an inch across the gasket surface as the engine warms up to operating temperature.
Diagnostic Solutions: Selling Brake Friction Replacements
A decade ago, an import shop’s profitability depended heavily on the routine replacement of spark plugs, timing belts, mufflers, shock absorbers, clutches and brake friction. Due to advancing vehicle technology, many of these profit centers have steeply declined or have altogether disappeared. One of the remaining exceptions is brake friction replacements.
Diagnostic Solutions: Solving Insufficient Fuel Problems
Solving cranking, no-fuel or insufficient-fuel driveability problems on late-model imports can be challenging, especially if a technician doesn’t take into account the way that modern fuel systems operate. Some vehicles, for example, limit vehicle speed by deactivating fuel injectors. In some rare cases, a miscalculation in vehicle speed can cause an insufficient fuel condition.
Wrangling in Jeep Spark Timing Dilemmas
Every once in a while I get a Diagnostic Dilemma that takes me back to the basics of how modern engine management systems work. This month’s happened to be a 1992 Jeep Wrangler equipped with the 4.0L engine and manual transmission. Of course, a vehicle of this vintage and configuration has to be about as basic as modern technology can get, right? Well, there are always exceptions.
Service Solutions: Lessons Learned Regarding ‘Old School’ Ignition Diagnosis
Recently, I’ve been confronted with driveability complaints on older vehicles that appear to defy conventional wisdom. Diagnosing such problems usually forces me to re-examine the fundamentals of engine
Diagnostic Solutions: Diagnosing Misfires
Although diagnosing misfires can be a tough assignment for any driveability technician, the diagnosis can be made much simpler if he understands the basics of misfire diagnosis. For example, when the first OBD II misfire monitor was first introduced in 1996, technicians were puzzled by problems with false misfire diagnostic trouble codes (DTCs). Case in point, vehicles being driven on washboard dirt roads began recording false misfires.
Diagnostic Dilemmas: Solving No-Code Performance Complaints
For many diagnostic techs, nothing is more discouraging and time-consuming than dealing with a no-code driveability complaint. Today’s second-generation On-Board Diagnostics II (OBD II) can be extremely sophisticated because the OBD II powertrain control modules (PCMs) in modern vehicles have far more computing capacity than did the older, pre-1996 OBD I vehicles. Nevertheless, we occasionally have to deal with a no-code performance complaint on a modern OBD II vehicle.
Tech Feature: Solving Steering Wander
As frustrating as diagnosing steering wander complaints might be, most can be solved by thoroughly inspecting the physical condition of the vehicle. In the following text, I’ll cover some of the most common causes of steering wander and how to detect them during an undercar inspection.
Diagostic Dilemmas: Lost in ‘The Diagnostic Woods’
This real-world case study of a 2002 Chevy S-10 pickup, a 1995 Buick and a 1995 Lincoln Town Car illustrates why “chasing” trouble codes can get you lost in the Diagnostic Woods.
Tech Feature: Performing the Complete Brake Job
The problem with routines is that we tend to – you guessed it – fall into a routine. Because the braking system on many modern imports is integrated into other systems like vehicle stability control (VSC) and traction control, modern braking systems must meet minimum levels of performance. For that reason alone, short-cutting a brake repair with substandard procedures and materials is a recipe for future comebacks.
Tech Feature: Winter Starting and Charging System Maintenance
Mid-winter is usually the coldest time of the year and, although modern vehicle technology has reduced many of the cold-weather starting problems that we faced just a short decade ago, it’s still important to keep your customers’ import vehicles in top shape for winter starting.