Auto Trans Diagnonsis - Solenoid, controller, or rebuid

[99 acord sedan 4cyl auto]

I have a 1999 Accord, 4 cyl ulev-vtec, automatic with 250,000 miles on the original powertrain. The car is bone stock, I bought it new. The transmission seems to be failing. The transmission slips when trying to shift into second gear - if it makes it into second gear it will shift HARD. If it does make it into second or third gear, it will randomly and without warning shift HARD back into first gear. This problem literally occurred overnight and without any warning. It drove normal at 6 am and at 2 pm the same day the problem occurred. Because of this problem, the vehicle is no longer drivable. I have pulled two codes; P0700 (Automatic Transmission Control System) and P0730 (Problem In Shift Control System).

 

The trans fluid is full, relatively clean, and free of odor. I drain and refill the fluid every 20,000 miles or so (about once per year). There are no leaks on the trans and visually it looks to be clean and in good overall condition. I live in Southern California so most cars are clean minus any leaky fluids.

 

I have checked the following per the Haynes Service Manual; 1) Mainshaft VSS, 2) Countershaft VSS, 3) Lock-up Control Solenoid/Shift Control Solenoid 'A', 4) Shift Control Solenoids 'B' and 'C', 5) Clutch Pressure Control Solendoids. I unfortunately have no information about the Transmission Control Module; where it is, how to test it, etc.

 

My test results are as follows:

1) Mainshaft VSS tested at 415 OHMs when removed fron the vehicle. This tested okay as the spec is listed at 400-600 OHMs.

2) Countershaft VSS tested at 416 OHMS when removed from the vehicle. This tested okay as the spec is listed at 400-600 OHMs.

3) Lockup Control Solenoid/Shift Control Solenoid 'A' tested at 30 OHMs. This is 20% higher than the Max allowed, spec is listed at 12-25 OHMs. Screens/Filters had minimal amount of clutch material trapped. Independent voltage applied to solenoids revealed that both operate (I can hear a 'click' when 12 volts are applied to terminal 1 and to terminal 2).

4) Shift Control Solenoids 'B' and 'C' tested at 16 OHMs each when removed from the vehicle. This tested okay as the spec is listed at 12-25 OHMs. There were no screens/filters to clean and the parts were fully intact.Independent voltage applied to solenoids revealed that both operate (I can hear a 'click' when 12 volts are applied to the individual terminals on solenoid 'B' and on solenoid 'C').

5) Clutch Pressure Control Solenoids tested at 5 ohms when removed from the vehicle. This tested okay, the spec is listed at 5 OHMs. A minimal amount of clutch material was trapped in the screens/filters.Independent voltage applied to solenoids revealed that both operate (I can hear a 'click' when 12 volts are applied to terminal 1 and to terminal 2).

 

My goal is to eliminate the sensors and solenoids (or any other low cost part) as possible problems before I replace the transmisison on this vehicle.

 

My first question is about item #3 above, the Lockup Control Solenoid/Shift Control Solenoid 'A' . The spec says the resistance should be between 12 and 25 OHMs, my part shows 30 OHMs. Is this variance enough to cause my problem? The dealer can order this part at a cost of $239.00 (not extremely expensive, but I don't want to spend the money on something I don't need). As you might be able to tell, I'm not just a parts swapper and refuse to spend money on things I don't need.

 

My second question; Can the Transmission Controller cause the problem I'm having? My Haynes manual has absolutely no information about this component, how to test it, or even where it's located.

 

I don't want to install a new/rebuilt transmission until I'm certain that it will solve my problem. It would be a lot of effort to replace the transmission only to find out it was an electronic controller that caused the problem.

 

My last question; Does anybody have any suggestions on other parts to eliminate as possible causes of this problem?

 

Thank you for your time and consideration, Anthony D, Temecula, California.

[Turtlehead]

I would recommend removing to shift solenoid for 1st and 2nd and clean the metal fliter screen that is under the solenoid (mounted on the transmission). This is an easy and a free thing to try. Sometimes it will solve the issue but other times it needs to be replaced. Of course this may not be the cause of your problem but it is the first thing to try. Good luck and let us know how you make out.

 

 

[Mille-16i]

Since it is a 99 my recomendation is a lil low tech but might help you some. there is really no good way for a home mechanic to test any ECU/TCU so I would say find a good wrecking yard and find a TCU (tranny control unit) off a vehicle with less millage than yours that HAS been wrecked that way you know it was driving when it died hopefully not to a cliff lol. you may want to pick up that part "Lockup Control Solenoid/Shift Control Solenoid 'A' " that way to might only be 50 bucks at a wrecking yard. your next option is to talk to a good tranny repair shop most can test all the electronics for a small fee think last time i owned a dodge auto Amco only charged 75 to test the electronics.

[99 acord sedan 4cyl auto]

I would recommend removing to shift solenoid for 1st and 2nd and clean the metal fliter screen that is under the solenoid (mounted on the transmission). This is an easy and a free thing to try. Sometimes it will solve the issue but other times it needs to be replaced. Of course this may not be the cause of your problem but it is the first thing to try. Good luck and let us know how you make out.

 

Thank you. I have check all three sets of solenoids and cleaned the filters/screens on them (only two sets of solenoids have filters/screens). There really wasn't an appreciable amount of clutch material in any of the solenoid filters/screens. I appreciate your input.

[99 acord sedan 4cyl auto]

Since it is a 99 my recomendation is a lil low tech but might help you some. there is really no good way for a home mechanic to test any ECU/TCU so I would say find a good wrecking yard and find a TCU (tranny control unit) off a vehicle with less millage than yours that HAS been wrecked that way you know it was driving when it died hopefully not to a cliff lol. you may want to pick up that part "Lockup Control Solenoid/Shift Control Solenoid 'A' " that way to might only be 50 bucks at a wrecking yard. your next option is to talk to a good tranny repair shop most can test all the electronics for a small fee think last time i owned a dodge auto Amco only charged 75 to test the electronics.

 

I like your ideas - but my Haynes manual has no information regarding the TCU (Transmission Control Unit) or TCM (Transmission Control Module), including where it's located, what it looks like, or how to check it. Do you know of another repair manual that has any information about the TCU/TCM?

 

There is an AAMCO shop about 20 miles from here. I'd really have to tow the vehicle there because it's not drivable over that distance. I'll call them on Monday and ask them how much a diagnstic will be.

 

I'm regrettably going to start looking for a junkyard transmission (hopefully with all the sensors and solenoids attached). I'm crossing my fingers hoping that it is the 'Lockup ControlSolenoid/Shift Control Solenoid A' that is causing my problem. If you (or anybody else) have any additional information on the TCU/TCM, it would be apreciated. I will update you soon. Thank you for your time and input.