Auto Transmission Stuck In Park
 

I have a 2004 Honda Accord LX with the 4 cylinder engine. Yesterday, my wife could not get the transmission out of park. We used the emergency latch release on the console. I have read through a lot of forums and threads and have verified a number of possible trouble-areas.

The brake lights work
The brake stop light switch was OK, but I replaced it anyway
I have 12 volts on the yellow lead going to the release solenoid.
The yellow black wire on the solenoid was not going to ground when the brake pedal was pushed.
I placed a ground on the ground lead and the release solenoid worked every time.
I verified continuity from the PCM pin 2 to the release solenoid ground wire
I pulled all five connectors on the PCM and reseated them - park release worked for about 10 minutes then stopped working again.
I hooked up my OBDII analyzer to confirm no trouble codes. The throttle position sensor was showing 9% at idle.
I confirmed that no fuses were blown
I pulled the throttle position sensor several times and reseated. I also applied a small drop of Deoxit on the 3 pins.
Whenever I pulled the TPS connector, the solenoid worked every time.
On the throttle position sensor, the 5 volt lead measured 5 volts, the position lead measured 0.5 volts at idle. The ground lead measured 0 volts.
The park solenoid release has been working for several hours now, but I suspect that the problem will come back.
My guess is that there is something that is intermittent on the PCM.

Is there some other checks that I can make. I would hate to replace the PCM and find that the problem is still there.

unlikely it's the PCM. usually the interlock solenoid starts going bad, working intermittently.

I would verify that ground supply from PCM is missing when foot is on brake.

I'm not sure what other conditions may be necessary for PCM to supply ground to interlock solenoid. Keyswitch input is possible. It may require keyswitch to be in Off position to enable shift from Park. I don't remember ever testing whether shift could occur w/ foot on brake, but keyswitch in On. I'm thinking it should shift.

A used PCM is not expensive, probaly < $50. Check ebay and car-part.com. Be sure to get an exact match for your PCM part.

I've had to replace PCM twice on my 94 Ex due to false DTC's; once was code 9 (distributor sensor0 and once for code 21 (Vtec pressure switch). PCM faults are not common, but neither are they rare.

good luck

Additional Info
 

Thanks for the recommendations. The car has been working good for two days now. When the problem was occurring, I verified that the PCM was not supplying a ground to the unlock solenoid when I pressed the brake pedal. I also verified that I had continuity in the wire from the PCM connector to the unlock solenoid connector.

When the problem was occurring, I could pull the connector to the throttle position sensor and the problem went away. I did this about 5 times to confirm. Seems that I recall that if the throttle position sensor shows greater than 11%, then the PCM will not send a ground to the unlock solenoid. My TPS was reading about 9% at idle and had 0.5 vdc on pin 2. That seems to be the correct reading per the manual.

My guess is that the problem will come back at some point. When it does, I will do the "remove TPS connector" again to see if that still fixes the problem. If it does, then either the TPS is sending the wrong signal (too much voltage to the PCM) or the PCM could be bad.

You might search this site for "TPS adjustment". I seem to remember someonoe developing a procedure. Shop manual assumes TPS comes w/ throttle body :rolleyes:

good luck

Still Working Ok
 

After one week, the park solenoid is still working fine. I would have to conclude that either I had a bad connection (possibly on the TPS connector) or one of the connectors going to the PCM. I also used my OBDII meter to clear all data from the PCM, so perhaps the PCM is showing a lower TPS % now and is not disabling the solenoid. I did put a drop of DeOxit on each of the TPS connector pins.

Stuck In Park Again
 

It has been three weeks and the Park release solenoid has been working fine. Two days ago, the Check Engine Light came on. My wife drove the car and came home. Tried the car again and the Check Engine Light was gone. This morning, my wife could not get the transmission out of park without using the manual release in the console. I disconnected the battery and waited 10 minutes. The problem is now gone again. Something must be getting set in the computer.

Any ideas as to how I can get to the root cause of the problem?

Code(s) should store......stop by almost any parts store and they should scan the codes for free....get the actual code and not their description and let us know what they are.

I checked for Pending Codes and Stored codes with my scanner and did not see any. There are some conditions where the check engine light will come on and then go off as the car is driven and the on-board computer does its fine tuning. I would have expected the check engine light from a couple of days ago to have a stored code, but it did not. That seems to make sense since the light went out on the next trip. From what I read, the computer has to recalibrate the Throttle position sensor if you reset the computer (along with other stuff). My guess is that I am going to see the stuck in park problem again in 2 to 3 weeks.

Codes Have Been Checked
 

I checked for Pending Codes and Stored codes with my scanner and did not see any. There are some conditions where the check engine light will come on and then go off as the car is driven and the on-board computer does its fine tuning. I would have expected the check engine light from a couple of days ago to have a stored code, but it did not. That seems to make sense since the light went out on the next trip. From what I read, the computer has to recalibrate the Throttle position sensor if you reset the computer (along with other stuff). My guess is that I am going to see the stuck in park problem again in 2 to 3 weeks.