Grease Monkey???

Recently I had to diagnose a Diagnostic Trouble code, B0183 05, referencing a sunload sensor fault. The service information stated that, “If no value is read at the time of fault, the HVAC Control Module uses 0 W/m² as intensity, 45° for elevation and -75° for azimuth.”

I reread it, repeatedly, realizing how much a “Grease Monkey” had to understand to effectively diagnose & repair a contemporary vehicle. The phrase “Grease Monkey” is not intended to be offensive. Rather, it draws upon the common perception that, due to the nature of the job, a mechanic, and especially an auto mechanic, will have grease marks or oil stains on his or her clothing. It also refers to a mechanic's ability to reach into small spaces and fix problems that might otherwise be impossible for an average individual to access.

Today’s service technician must understand thermodynamics—the movement of heat—to effectively diagnose a latent-heat exchange problem at a condenser. Imagine the customer’s surprise if you told him, “The diathermal walls of the forward heat exchanger are displaying the consequences of Zeroth’s Law which states that no heat will flow between two objects that are at the same temperature.”

Right.

“In other words, you have a clogged condenser.

Or how about the customer who thinks that you have this remarkable “tool” that tells you what to replace to restore his machine to proper performance? All you must do is plug it into the diagnostic connector, right?

So, you’re diagnosing a P1101, an intake airflow system performance concern. So, this is what you read in the manufacturer’s service information about the concern:

The intake flow rationality diagnostic provides the within-range rationality check for the mass air flow (MAF), manifold absolute pressure (MAP), and the throttle position sensors. This is an explicit model-based diagnostic containing 4 separate models for the intake system.

·         The throttle model describes the flow through the throttle body and is used to estimate the MAF through the throttle body as a function of barometric pressure (BARO), throttle position, intake air temperature (IAT), and estimated MAP. The information from this model is displayed on the scan tool as the MAF Performance Test parameter.

·         The first intake manifold model describes the intake manifold and is used to estimate MAP as a function of the MAF into the manifold from the throttle body and the MAF out of the manifold caused by engine pumping. The flow into the manifold from the throttle uses the MAF estimate calculated from the above throttle model. The information from this model is displayed on the scan tool as the MAP Performance Test 1 parameter.

·         The second intake manifold model is identical to the first intake manifold model except that the MAF sensor measurement is used instead of the throttle model estimate for the throttle air input. The information from this model is displayed on the scan tool as the MAP Performance Test 2 parameter.

·         The fourth model is created from the combination and additional calculations of the throttle model and the first intake manifold model. The information from this model is displayed on the scan tool as the Throttle Position Performance Test parameter.

The estimates of MAF and MAP obtained from this system of models and calculations are then compared to the actual measured values from the MAF, MAP, and the throttle position sensors and to each other to determine the appropriate DTC to fail.

As a technician, you are expected to know that the P1101 is caused from a failed throttle model test, a passed first intake manifold model, a failed second intake manifold model and a failed fourth model. Now, since you know that the engine controller detected that the actual measured airflow from the MAF, MAP, and throttle position sensors is not within range of the calculated airflow that is derived from the system of models for greater than 2 s, you must determine the root cause of the concern. You have a remarkable tool, all right—it’s called your brain. And it doesn’t plug into the diagnostic connector of the vehicle (at least not yet)!

Computer programming can be an everyday occurrence for the typical shop technician. These days, the programming is sequential, meaning that multiple control modules will be updated at the same time to prevent any conflicts that could result due to modules having incompatible versions of programming. Several computers will have a setup procedure to relearn the values of vehicle systems and components. Modules may require a configuration procedure that sets a security code configuring the control module to the specific vehicle, which helps prevent theft of the module.

The technician of today must be adept at electrical diagnosis which can only come with the understanding of Ohm’s Law, Kirchhoff’s Law, and such terms as “resistance,” “conductance,” “susceptance,” “admittance” and “inductive reactance,” just to name a few. An oscilloscope can be a valuable diagnostic tool as it provides a graphic view of the waveform.

Consider a starter motor as it allows moderate current flow as the engine crankshaft pushes a piston up in its chamber and then a higher current as we’re compressing the gases in the cylinder. The starter motor creates an Electromotive Force (EMF), increasing with speed, in the opposite direction to the voltage supplying it. This Back-EMF reduces the current flowing into the motor. The heavier the load on the motor, the slower it runs, so the smaller the back-EMF, the higher the current. EMF and Counter-EMF are more terms the technician is familiar with.

So, what is a Grease-Monkey? Climb into your time machine to visit the industrial revolution of Great Britain to see children greasing the massive rotating axles used to transfer power from one primary steam engine to all the units on the factory floor. The children, capable of climbing into small places, became covered with grease. Now you’ve seen a grease-monkey.

So, back to my first question:

 If 0 W/m² is intensity, and 45° for elevation and -75° for azimuth, is it morning, noon or night from your location (assume, of course, that azimuth is the sun’s location on a horizontal plane running from east to west?