Read Codes While Running?

I have a 1990 5.7 out of a police car that I put into a Land Cruiser. I have the original computer, etc. I modified the computer for a flash chip. I made some minor changes to account for our E95 gas and a minor tweak to the spark table to stop detonation at a certain MAP... Anyway, after a couple thousand miles I am having trouble. Coming down from the mountains last summer the check engine light came on and the computer went into limp home mode. I pulled over and shut the engine off. When I turned it back on the light was out and the engine ran fine. Fast forward to now and this is a frequent event. Some trips it happens several times. I did notice what triggered it faster. I was climbing a mountain pass at 70 and needed wide open throttle to maintain speed (a lifted FJ40 has the aerodynamics of a barn door) it seems to happen quickly when in 4th gear. If I slow and drop out of OD it doesn't seem to happen. However this also occurs when I would not expect it at all, not at full throttle, etc. The issue doesn't happen when I am just driving around near my home, only on longer trips.

The problem is that the issue transitory and resets when I restart the engine so I have no idea what is triggering it.

Is there any way to trigger the fault codes to flash when the engine is running? I don't think so but wanted to ask.
Is there any add on devices that would capture the codes while running?

Short of those options can you all think of some troubleshooting steps to diagnose the root cause? I really don't want to have my laptop connected and data log while on long four wheeling trips. That will kill the laptop very quickly.

Thanks

TunerPro RT can scan for codes real time. For example, unplugging the vacuum hose to the MAP sensor with the engine running will trigger a code in TunerPro RT.


dave w

As Dave said Tuner Pro, or a scanner can see codes while the engine is running. Even better to datalog a session or three and see what was happening just previous to the code(s) being set.

Hiya Dave!

I know it can read codes. I was trying to avoid having the laptop with me on whole day wheeling trips, though. I don't remember if Tuner Pro can connect with the engine already running or does it need to be on before I start the engine? I might be able to take the laptop with me in a bag then hook it up and turn it on after the light comes on.

That isn't a bad idea Six Shooter. I have not done any data logging since I finished the last tune. Might be good to see how it's running.

You can connect the laptop any time.