Subaru Outback Forums banner

1 - 5 of 5 Posts

·
Registered
Joined
·
2 Posts
Discussion Starter #1
Hi Folks, new to Outbacks (but not Subarus) since my bro-law bought a 2006 H6 Outback last week wholesale from a car yard for him and his son.
Its showing codes that seem to point to a valve body problem in the 5EAT. Can you tell me what you think?
The Story:
The problems started when I replaced the cheap and nasty Indonesian radiator that was in it. The reason was that the driver's side trans cooler fitting was leaking ATF and the cheap design looked like it could let coolant into the trans lines through a split o-ring on the metal connector in the bottom tank (the radiator looked brand new!)
I put a decent quality radiator in it (I'm an ex-mechanic) and did a minor trans service by dumping the fluid out the cooler line while I was at it.

Bro-law reckons later that same day it started flashing dash warning lights and it's coming up with these codes on my OBDII scanner:
P1799 - says check with Subaru
P1798 - Gear 1 Engine Braking
P0771 - Shift Solenoid E Performance Stuck Off
P0770 - Transmission Control System

The transmission shop I rang says it needs a new genuine valve body for $3k+ because parts aren't sold separately. The guy said eventually it will get stuck in limp mode and be undriveable until the repair is done. He also said there was no connection between me changing the fluid (I put Penrite Fully Synthetic ATF in), it's just a coincidence.
So my question is, have you seen this problem before, and is there a cheaper option to repair this?
Thanks, Dave
 

·
Registered
Joined
·
16,405 Posts
it's coming up with these codes on my OBDII scanner:
P1799 - says check with Subaru
P1798 - Gear 1 Engine Braking
P0771 - Shift Solenoid E Performance Stuck Off
P0770 - Transmission Control System
The key code among the four is probably the P0771.

"DTC P0771 SHIFT SOLENOID “E” PERFORMANCE OR STUCK OFF DTC DETECTING CONDITION:
Output signal value of low coast brake solenoid and oil pressure does not match."

The low coast brake is activated when in manually-selected 1st or 2nd gear.

In the 5EAT, there's a pressure switch on the valve body that monitors hydraulic pressure going to the brake. When the TCM turns on the low coast brake solenoid to apply hydraulic system line pressure to the brake clutch, the TCM checks the signal from the switch. If the switch doesn't confirm the high line pressure, the TCM triggers the P0771 fault.

In this case, the problem could the solenoid, a related spool valve, the pressure switch, or the wiring to either the solenoid or switch. A bad contact in a transmission harness connector could be a factor.

. . . is there a cheaper option to repair this?
With the possible exception of the transfer duty solenoid, as far as I know there are no Subaru or aftermarket new parts for the valve body. If the problem isn't in the wiring (where it might be repairable), then the whole valve body is replaced. A recycled unit might be an option. If the low coast brake solenoid itself is found to be faulty, it might be possible to replace it with a good one from an otherwise non-functioning valve body.

Sometimes a valve or line could be clogged/binding for some reason and changing the ATF a few times clears it. In a case earlier this year involving the torque converter lock-up function, the ATF had been changed several times, yet the problem remained. All the FSM tests checked out, and that left the valve body itself. A used valve body was installed but it had its own problems (a different function was faulty). The original valve body was put back in, and the transmission worked again. No explanation other than something that was preventing the lock-up system from engaging that could not be flushed out with the ATF changes, was probably dislodged/drained out when the valve body was removed.

The FSM has a troubleshooting guide that includes checking the wiring and electrical signals. Subaru FSMs, as well as related documentation (Mechanism & Function, TSBs, etc.) are available at https://techinfo.subaru.com/stis/#/login
 

·
Registered
Joined
·
12,371 Posts
Check for dented pan or signs of previous work/replacement at the pan mating surface/sealant. If there's signs there, check wiring for damage or VOM it.

Price a new one, if they're ugly price a used one. They're sometimes problematic, but not often enough to worry about installing a used one. i'd do it if the price was a major hurdle on a new one.
 

·
Registered
Joined
·
2 Posts
Discussion Starter #4
Thanks for the replies.
BTW I'm in South Australia.
One thing I must mention is that if you clear the codes and drive forwards in D the problem doesn't occur. The lights come on as soon as you drive a little in reserve or use the paddle shifts (which probably explains the brake solenoid fault shows up).
 

·
Premium Member
Joined
·
232 Posts
This could be a long shot ... if the car is an '05 model year there's a transmission software (TCU) update available at the dealership to address P1799 & P0771. I've attached the Subaru PDF doco to this post. It is written for the USA market but helped out with my vehicle (imported to NZ from Japan) on a different issue. It may not apply to you bro-law's car but I noticed a friends subaru has a 2006 rego sticker but the electronic parts catalog (such as partsouq.com) matched the chassis number to the '05 model year.
 

Attachments

1 - 5 of 5 Posts
Top