Starts then Stalls
As test drives would go, this one did not go quite as expected. With any engine rebuild, there are always unknowns. Starting the engine in the garage and letting it run at idle is one thing, but on the road and under a load is another.
I had a plan. The first test drive would be dinner out with my wife to celebrate. There is a great sushi restaurant nearby. I knew it needed fuel so we could stop on the way. But less than a block down the road, my excitement quickly turned into panic. At first, it was just a sputter. Ok, I thought, we’re just low on fuel. The gauge was sitting below empty, but surely I had enough to make it to the gas station a few miles away.
After the second and third sputter, I quickly made a U-turn before things got worse. Then I returned home and parked the car. I know I had at least a gallon’s worth of gas in the garage for the lawnmower, which should be just enough to make it less than five miles to the nearest gas station. So I added that in, which barely moved the gas gauge.
My adrenaline is still pumping because I want to see this thing on the road and running. But to complicate things even more somewhere along the short trip, the check engine light came on. I quickly clear any faults and attempt a second start. The engine fires and then dies. What the hell!
Ok, maybe there is still not enough fuel in the tank. I run to the shed and grab the five-gallon can. Jump into my other running, driving car and head to the station. I put five gallons worth in, which should be more than sufficient.
It should start this time.
After dinner, I returned home, determined to give it one more try before giving up for the night. After trying to start it a couple of times only to have it die, I finally just held the gas pedal down at around 6,000 RPM for a few seconds in an attempt to keep it from stalling. Viola! It stabilizes at idle.
Not to miss an opportunity, I closed everything up and headed out for one more test drive. At this time, it’s after midnight, so traffic is light. But the great news is whatever I did it no longer stalls. Not sure how exactly but I’m not trying to figure it out at this point. Because now it’s working fine. So my first stop is the gas station.
Code 2
Immediately I notice a few things. The shifting is horrible. The transition from 1st gear to 2nd is taking too long, and once it finally shifts, it’s rough. The rpm is way up, and it feels clunky. 2nd to 3rd is not much better; only there is no time between shifts. The engine power also feels unimpressive. There is no power. It’s slow and sluggish.
I am able to make it to the gas station, nevertheless, and fill the tank completely.
After an hour of driving around the neighborhood back roads at low and high speeds, I return home satisfied that, for the most part, it did what it was supposed to do. The engine temperature was steady at 190 degrees, which is excellent. Remember this is what started this whole mess in the first place. The check engine light did come back on, but that is no surprise to me considering the performance.
The following day the first thing on my troubleshooting list was to check my OBDElevens history report. I could see right away there were a lot of trouble codes pointing to the no start issue and the overall performance or lack thereof. Needless to say, the low fuel was not the cause, as I would find out later.
P1857
But out of all the codes, I see a transmission fault. P1857 load signal error. I immediately start searching the internet for possible causes and solutions. I quickly find a thread post from Audiforums.com. The post is titled P1857. In the post, the guy mentions that the Electronic Control Module or the Transmission Control Module could be the cause of the problem. Well, it’s a transmission code, so I will start with the TCM as a possible cause. So I do a quick Google search for any TCM issues regarding a Volkswagen Passat – 2005 year model, and I quickly find a post from passatworld.com titled Electrical Issues Passat B5 TCM? ECU?
I read through the post, and the responses varied between the ECU being the problem or the TCU or perhaps even the Climate Control Module. In his post, he talks about the instrument cluster lights blinking. And he went as far as to take it to a Volkswagen dealership, and their diagnostic test called for the TCU to be replaced. I did not have any blinking instrument cluster lights, but I did have a brake warning light appear out of nowhere, but after restarting the car, it went away. Which I thought was odd. But the further I read, I finally found something that made sense. He mentioned that his passenger seat had flooded one day, and that is where the TCM is located.
Light bulb! This could be the problem. Just a week or two earlier, I had a similar incident. I parked my car outside overnight without the hood or rain tray installed, and just my luck it rained that night. The next morning I went out to check on it, and the passenger side was full of water. I quickly vacuumed out all of the water, but it did not occur to me that the TCM could also have gotten wet.
I also spoke with a local transmission specialist about the shifting issue. It turns out VW automatic transmissions are very finicky when it comes to the type of ATF fluid used. And of course, I stupidly make the mistake of using the wrong kind of fluid in an attempt to save a few dollars.
He advised me to flush the transmission right away. Ok, this is not great news to hear, but it is not the worst either. This is an easy fix. Since I have to source and order a replacement TCU, this will give me an opportunity to remove the TCU and source the correct transmission fluid and find a more efficient fill method. On the other hand, the TCU is not a part that you want to go bad. A new replacement can cost upwards of $1600. Luckily I was able to find a replacement on eBay for $80.
Transmission Control Module
Removing the old TCU is straightforward. It only requires removing the front passenger seat, the right forward kick panel, and the right lower b-pillar trim. After that, it is simply partially pulling up the carpet to gain access to the housing case. Once I had access to it, I did call Volkswagen to verify that the TCU installed is the correct part number. So when I ordered the new one, it was the correct one. The VW parts department did confirm that it was the correct one. She did also say that the replacement TCU would have to be flashed since the VIN would not match.
Once the replacement part arrived I took a chance anyway and installed it without flashing it.
I installed the TCU first before flushing the transmission. This way, I could clear any fault codes before driving the vehicle and get the fluid up to operating temperature before draining and servicing.
As I was raising the vehicle to drain the transmission, I discovered another obvious and almost certain cause for the poor performance and no start issues. The charge pipe from the inner cooler had come loose. Bingo! Amazing something that simple could cause so many problems.
Once I had that connected, I continued flushing the transmission. The correct fluid for the 5HP-19 transmission is Pentosin ATF1. It is expensive compared to other off the shelf fluids. It costs around $23 to $27 a quart. And I needed to flush it at least twice using at least 5 quarts each flush. So take note and always use the recommended fluid/part. It will save you a lot of hassle in the long run.
As far as the TCU swap, it was less maintenance intensive. Once I had access to it, all I had to do was release the terminal clamp and separate it from the TCU. As with any electrical work, always be sure to disconnect the battery first. Installation was the reverse of removal. I inspected the area for any corroded or bare wiring before closing everything up as well as the terminal connector. Everything seemed to be ok, and the area was dry.
The transmission flush went quickly with the aid of a Quick Jack and pressurized filler tank from Schwaben. The only thing left to do now is getting it buttoned up and back out on the road for another test drive.