1994 Honda Accord EX - F22b1 Engine, 2.2L VTEC - 250K mileage

Hello everyone, I am new to this forum, but I have a dreaded transmission problem that hopefully this forum can solve before it goes to the dealership.

Problems:
1. When warmed up, the car is stuck in park and will not shift out when pressing the brake. When cold, however, the car will shift out (I can hear the interlocking unit working). Brake lights are working 100%.
2. The car has some shifting problems, especially shifting late - when I put the car at 45MPH under cruise, the car switches, not hunts, between 3rd and 4th gear.
3. The engine is idling low and has a hesitation/misfire every time I pull away from a stop.

No codes from the transmission or CEL light.

This problem started after I left the car in heavy rain for 3 straight days (regretting that now). I am thinking something was shorted. Looking through my service manual, I am tending to think it is the Transmission Control Module. I pulled it out from the passenger footwell and cracked it open - looks brand new with no burned out resistors or capacitors (problem with the early 90's Accords).

I am tempted to pull the trigger on ordering a used TCM on Ebay, and or just giving it to the dealership for diagnosis. Anything will help on narrowing this problem down. Thanks!

 

Some possible culprits:

• Throttle position sensor - Try unplugging the connector to the TPS, you’ll get a Check Engine Light; but, see if you can shift out of Park when the issue comes up again.

• TCM (Transmission Control Module)

This is how the shift position interlock works:
When you push the brake pedal, battery voltage is sent through a GRN/WHT wire to the TCM. If, at the same time, you do not push the accelerator pedal, a low voltage signal is sent from the TPS through a RED/BLK wire to the TCM. The TCM then applies voltage through a WHT/GRN wire to the shift lock circuit in the interlock control unit. If the shift lever is in the PARK position, ground is provided to the shift lock solenoid. The solenoid is then energized allowing the shift lever to be moved from the PARK position.

 

Thank you for your reply. That's interesting what you said there, because I purchased a TPS sensor thinking it was it. I measured the voltage coming from the middle wire while it is plugged in, and I was getting not 0.5V to 4.5V at WOT (normal range), but rather 1.0V to 3.4V at WOT. It is a linear progression, which leads me to believe that either the TPS is fine and needs adjustment, or it is the TCM.

 

The TPS has the following 3 wires:

• Terminal no. 1 (Grn/Blu) - Sensor ground (-) coming from ECM (Engine Control Module)
• Terminal no. 3 (Yel/Blu) - Reference voltage (5V) coming from ECM (Engine Control Module)
• Terminal no. 2 (Red/Blk) - TPS output (voltage varies depending on position of throttle) to both the ECM and TCM

If the TPS voltage output was at 1.0 volts with the throttle fully closed, the TCM will thinks the accelerator is depressed and the throttle is open and prevents the shift lock solenoid from energizing (you won’t be able to shift out of Park).


The TCM (Transmission Control Module) does not affect the TPS output on the Red/Blk wire.

 

Hmm, that's interesting. I have yet to confirm this but I think in the morning, the voltage is correct at 0.5V. Hence why the interlocking unit works. It doesn't work after the first drive. Redbull-1, are you thinking the TCM is fine? Or should I look into substituting the TCM to isolate the issue. Thank you for your help.

 

Can't rule the TCM out yet; but, based on what you wrote, there is no definitive indication the TCM is the issue yet.

There is an issue with the TPS voltage output if it is 1.0V with the throttle fully closed (cold or warm). Try to resolve that first.

 

Bingo - almost. I haven't had time to install the TPS yet, but I was able to unplug the TPS and install the new one hanging (not installed). The shift lock worked instantaneously.

I also tested the voltage coming out of the center wire with the new TPS connected, and it is ranging from 0.4V to 4.0V. I can easily adjust the closed-throttle voltage so it reads 0.5V, but do you think the 4.0V is an issue? Probably won't get WOT, but I just want the car to get me from A to B.

Also, if and when I do replace the TPS, do you know if this would fix my transmission shifting troubles? I have heard that TPS replacements would fix idle and transmission issues. I will clean the throttle body while I am in there.

I should know more tomorrow when I install the TPS. It will be a joy to install.. especially with the bald head screws Honda put on them.

 

I am getting some new information now (some conflicting). There is a throttle stop screw that is not adjustable according to my service manual, but some said that you use an allen wrench to adjust the range of the TPS voltages. Would I turn that down since my voltage range is so narrow (0.8V to 3.8V, measured again today)?

Some are saying NOT to touch it, but I am thinking otherwise. I would much rather adjust something then crack open the TB and replace a part I don't need if fine. Help?

 

I'm a bit late to this thread and confused as well....it is me not anyone else.

The TPS has slotted holes in it. From the factory there are pop rivet bolts that hold it in place. Most cut a slot in the head to remove. Then when you install the new one, use the chart (~.5 closed to ~4.5 wot) to get the new one in the proper position/adjustment and then tighten it down.

 

Yes, you'll find a few threads on the internet that some people try to use the throttle stop screw to adjust the TPS.

As you can read in this other thread by JimBlake (post #5), " The throttle plate must close completely, and that little stop screw is used to (just barely) prevent the throttle plate from wedging stuck closed."

https://www.hondaaccordforum.com/for...bracket-60185/

I would not recommend messing with the throttle stop screw.

In addition, what you previously described sounds like a bad TPS, as the voltage output is different when cold vs hot. So, it is unlikely just an adjustment of the old TPS will fix the issue.

To get the pop rivet bolts/shear bolts off, you can either do like most people and cut slots in the head and then turn it off with a screwdriver. An alternative is to use a center punch and make an indentation on the head and then holding the punch at an angle, use a hammer and punch to turn the screw out (counter-clockwise).

To install the new TPS, re-use the old bolts or try to find some M5-0.8 x 16mm bolts.