P0506 Code but feels like a transmission issue

Maintenance/Repairs
1

I have a 2003 Honda Accord with 207,000 miles on it. It’s been doing the following:

  • From Reverse to Drive, there’s a 2 - 3 second pause before it engages
  • Sometimes when driving at higher speeds (55 - 70mph) then slowing down for a light or an exit, the car will sort of lurch/jerk around 30mph on the slow down. It’s very noticeable.
  • Check Engine light has been coming on off for months. I thought it was a gas cap issue but the mechanic said it’s a P0506 code.
  • Hard shifting in my day-to-day driving
  • Just fyi, we had the transmission rebuilt a year and a half ago. It’s under warranty for another 5 months.

We’ve taken it to the transmission shop twice and they said they don’t feel the things we describe and are getting no codes. We’ve taken it to the Honda dealer twice and the honda mechanic did a software update that didn’t fix the issue. I took it back and then he said he felt the hard shift/delay from R to D and that it is a transmission issue because the engine wouldn’t be engaged at all from R to D. The CE light wasn’t on for that visit and wasn’t giving a code but then the CE light came back on when I was on my way back to the transmission shop. I read that there are specific things to do to try to clear the P0506 code (clean the throttle body, check for vacuum leaks, etc.) but our Honda dealer didn’t do any of those things.

Has anyone experienced this kind of thing? Is there an engine issue related to the P0506 code that could make my car do these things but feel like a transmission issue even if it’s not (since I’m not getting any transmission codes)? Could I have two separate issues - whatever is triggering the P0506 code and then whatever is making the car shift hard, slow to engage, and jerk when slowing down? Any advice on how to talk to the mechanics about the issue? Our honda mechanic is noticeably agitated with us now when we call about the issue. My transmission guy told me since they’re not feeling anything or getting any codes, the only thing left for them to do is take out the transmission. I’m at a loss and feel like I’m wasting their time, but there’s definitely something wrong.

2

Is there some reason why you don’t want to address the specifics of that trouble code?

If I was in your situation, I would replace the O2 sensors on the exhaust system, and (possibly) clean the Idle Air Control Valve in order to see if the problem is resolved and if the CEL turns itself off before delving into anything involving the transmission.

3

The P0506 code has to be addressed first. Idle Air Control System RPM Lower Than Expected.

If the Idle speed is too low, and you shift from R to D, the pump within the transmission isn’t turning fast enough to make the clutches engage so there’s a delayed shift.

If you’re driving at speed, and then suddenly let off the accelerator and the engine goes to idle, and the idle is too low, the transmission control module will see low line pressure. The TCM will then raise the line pressures to prevent damage to the transmission and this causes hard shifting.

The transmission function in your vehicle is very complicated.

I just went through all this on the wife’s Accord.

If the D4 shift position on the instrument cluster isn’t flashing, there’s nothing wrong with the transmission.

Tester

4

Thanks for the information, VDCdriver and Tester. The only reason the trouble code issue hasn’t been addressed is because the Honda dealership mechanic thinks we have a transmission issue. He said he cleared the code with the software update, and when we let him know the code came back on (but went off again) he didn’t seem to think there was a problem (I guess because the CEL wasn’t staying on?). You both confirm my hunch that we need to deal with the CEL and then if there’s still hard shifting, etc., move forward from there. Thanks!