Magazine for the auto service professional
Issue link: http://asp.epubxp.com/i/780462
26 | ASP February 2017 Technical cycles the code will clear automatically. But if the test fails again during those cycles then the DTC will set and the MIL will be illuminated. is mode should always be looked at before the codes are cleared as this information is cleared when a Mode $04 reset is performed. Pending codes that are unrelated to the hard code that turned on the MIL should be noted and mentioned to the customer before any repairs are performed. Mode $08... Request control of on-board system, test or component. Mode $08 is intended to allow the scan tool to perform some bidirectional control of an onboard test or component. Typically it will allow you to seal the evaporative system to check for leak testing. is mode is really hit or miss and doesn't usually do anything. Mode $09... Request vehicle information. Mode $09 provides the vehicle's VIN, calibra- tion IDs, calibration verification numbers, and other useful data that includes in-use performance tracking. In-use performance tracking logs the number of times that spe- cific component monitors (catalysts, primary 02's, EGR, AIR, and evaporative system) ran to completion, and it also shows how many times the conditions to run that monitor were enabled and the total number of engine starts. is information is useful in verifying a repair and knowing if something was inhibiting the enabling conditions (failing thermostats are very common at stopping monitors without trouble codes being gener- ated). I like to look at this area to make sure that the monitor counters are increasing. If they seem to be fixed or display a very low number relative to the vehicle age or mileage, I am often suspicious of a car that has some form of tune or non-factory PCM software and this can help in your diagnostics. Mode $0A (10)... Emission-related DTC with permanent status. We know that the MIL light can be turned off either by passing the prescribed number of tests without a fault reoccurring or having the fault repaired and using Mode $04 to clear the MIL. But just because you or someone else has turned off the MIL, that doesn't mean that the PCM has forgotten that any codes were set. Starting on some 2009s and all 2010 and up vehicles, Mode $0A remembers that there was a fault serious enough to request the illumination of the MIL and keeps this information in a non- volatile random access memory (NVRAM). is NVRAM can't be erased by using Mode $03 or a battery disconnect and it can hold up to four codes for over a year until the diagnostic executive part of the PCM erases it after it performs a test verifying that it's been repaired (typically passing three consecutive trips without fault). Finishing up and putting this all in practi- cal terms, and using it in the shop. Here is a scenario that I have encountered more than once. It's a 2011 Ford Escape with a 3.0 V6. e customer's issue is that it drives fine but the MIL is on. e first thing I do is hook up an OBD-II capable scanner and look for codes. At this point I have used Mode $01 and Mode $03. It displays the code P0420, a catalytic efficiency code for bank 1. I then look at the freeze frame data (making sure that freeze frame data is for the P0420 code) and check the operating conditions when the MIL was turned on. e Data in Mode $02 ( freeze frame) shows me that the vehicle was at operating tempera- ture, in closed loop, on the highway and the fuel trims on both banks were at about +/-5% (which is OK). From this point I will go to Mahle provides an OBD diagnostic report that pro- vides not only all the Mode $06 data, but codes as well. This is very helpful in explaining to customers that other systems may be close to failing or shut off by certain codes that already exist.