Skoolies post a lot about converting a school bus but very little about engine error codes. Or about the mechanical part of the school bus. I guess maybe thats because they have professionals work on their buses. I don’t really know. But we have a 22 year old bus and that means not many mechanics have experience working on them.
During our first long trip in our bus we had a lot of starting problems. It never left us stranded but it sure acted like it was going to a few times. Along the way I worked on fixing the problem. Eventually I zeroed in on the main issue, the glow plug solenoid assembly.
It was my fault that I spent $900 on repairs during our trip, when what was wrong was a $100 part that I could fix. What I did was over think the issue. I got fancy and thought it was the injection system. The parts I had replaced were old, and it was good to replace them, so it wasn’t a total waste of money. However it didn’t solve the problem.
This over-thinking is also the reason most of the mechanics I talked to didn’t know how to clear engine codes on a 22 year old school bus.
After the trip I did more work on making the bus reliable. I went through the engine error codes. You do this by turning the key on and pressing the Diag. button. The “Warm Engine” light will flash a number of times, in 3 digit sequences. For example the “No Fault Detected” code is 111, and thats where they start. All other codes are higher than 111.
Active and Inactive Engine Error Codes
There are “active” codes and “inactive” codes. When the codes flash on the dash they start with the active codes, and then flash the inactive codes. If a problem still exists the code will be active. Once the problem is resolved the ECM will remember the error code and store it as an Inactive code.
The problem is, the dash will indicate there are engine error codes when you start the bus. These codes can be active or inactive. The only way to check is to go through the diagnosis process. And who wants to do that every time you start the bus?
What you need to do is clear all the inactive engine error codes. The problem is there is no clear way of doing this. If you ask “most” mechanics they will tell you that a laptop or code scanner is needed to clear the codes. And “most” mechanics will be wrong.
Clearing Inactive Engine Error Codes
I have a Scan Guage-D that reads and clears codes. However it will not read or clear inactive engine error codes.
It only makes sense that such a simple error code display system, counting flashing lights on the dash, would have an equally simple way of clearing the codes. After all, this is a 1995 International 3800. Back then a LOT of mechanics didn’t have fancy scan tools or laptops. This system was designed so a mechanic with a code book and hand tools could diagnose and fix this truck.
It is important to remember that Active codes cannot be cleared until the faulty condition is corrected. But you can clear inactive codes manually WITHOUT the use of a scan tool or laptop.
To clear inactive codes:
Press engine diag. button and hold down, turn key on but do not start.
Depress accelerator pedal all the way to the floor 3 times quickly.
Turn key off, release engine diag. button, wait 20 or 30 seconds to allow ECM time to clear codes.
To verify all the codes have been cleared, turn key on and press the Diag. Button. You should get only one Active codes, that being 111 (No Fault Detected) and no inactive codes. Sometimes you have to run through the clearing procedure more than once for it to take, and don’t forget to wait the 30 seconds before checking.
Alternate Method of Clearing Engine Error Codes:
I have not tried this method but I have read that if you first disconnect the battery ground cable, then the positive cable. Make sure you disconnect and isolate the battery ground cable for at least one minute. Then connect the cables again and check to see if the codes have been erased. This is a bit more drastic but it should clear the inactive engine error codes.