Engine Controls - Basic Diagnostic Procedures: Introduction
The following diagnostic steps will help prevent overlooking a simple problem. This is also where to begin diagnosis for a no-start condition.
The first step in diagnosing any driveability problem is verifying the customer's complaint with a test drive under the conditions the problem reportedly occurred.
Before entering self-diagnostics, perform a careful and complete visual inspection. Most engine control problems result from mechanical breakdowns, poor electrical connections, or damaged/misrouted vacuum hoses. Before condemning the computerized system, perform each test listed in this article.
CAUTION:
On MDX models, the Powertrain Control Module (PCM) overwrites data and monitors the EVAP system for up to 60 minutes after the ignition is turned off. Jumping the SCS line after turning ignition off cancels this function. Disconnecting the PCM during this function, without jumping the SCS line first, can damage the PCM. When removing/installing PCM or disconnecting PCM connectors, steps 1 through 3 must be followed to protect the PCM from damage, or wait at least 60 minutes before disconnecting. Perform the following:
- With ignition on, connect the Honda PGM Tester or the Honda Diagnostic System (HDS) to the data link connector (DLC), and go into any of the live data screens.
- Turn ignition off.
- Turn the Honda PGM Tester off or close the HDS and then back on. Go to the SCS mode and follow the screens to ground the 16-pin DLC.
NOTE:
Perform all voltage tests with a Digital Volt-Ohmmeter (DVOM) with a minimum 10-megohm input impedance, unless stated otherwise in test procedure.