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p3424
03-05-2017, 08:00 PM
Just sharing my thoughts about these particular OBD codes related to the 722.6 transmission.

On a couple trips involving using lower gear to prevent the brakes from overheating on prolonged downhills, a couple of my MB with the 5 speed 722.6 transmission lite up the check engine light sometimes later, causing anxiety on these long cross country trips...

2000 E320 4matic going down Piks Peak
2006 Dodge Sprinter 2500 going down a single long hill

After the initial panic to check the code:

2000 E320 4matic OBD code p0700
2006 Dodge sprinter 2500 OBD code P2A00, P2091, P2511

After reset, the OBD stayed clear after the initial incident

I had stayed well below red line on both cases. Since the check engine light had stayed off and no pending code month after, I can only conclude these are one time transmission related codes. Which lead to the question, don't they have hills in Germany?

Aqua Puttana
03-05-2017, 08:20 PM
Not that you asked...

I avoid using radical downshift and higher RPM engine braking for hills. I prefer to use a high(er) gear and apply my brakes for harder braking, relatively short time periods to help to control my speed as necessary.

I feel it isn't good for the engine to "float" at higher RPM's. There's a big difference in the engine firing and working while at higher RPM's as opposed to a no power compression stroke while engine braking.

I recall a thread here where an owner had engine failure. His operation included engine braking on a long hill at high RPM. I have no data as to whether his engine braking contributed to the failure. Even so, I still avoid it.

:2cents: vic

lindenengineering
03-06-2017, 12:27 AM
Just sharing my thoughts about these particular OBD codes related to the 722.6 transmission.

On a couple trips involving using lower gear to prevent the brakes from overheating on prolonged downhills, a couple of my MB with the 5 speed 722.6 transmission lite up the check engine light sometimes later, causing anxiety on these long cross country trips...

2000 E320 4matic going down Piks Peak
2006 Dodge Sprinter 2500 going down a single long hill

After the initial panic to check the code:

2000 E320 4matic OBD code p0700
2006 Dodge sprinter 2500 OBD code P2A00, P2091, P2511

After reset, the OBD stayed clear after the initial incident

I had stayed well below red line on both cases. Since the check engine light had stayed off and no pending code month after, I can only conclude these are one time transmission related codes. Which lead to the question, don't they have hills in Germany?

I will deal with the E class transmission fault first
P0700 is a MIL request for a transmission control fault.
Normally it goes with other possible faults that are about to be recorded.
Possibly high temp warning! Who knows!!
It begs the question as to when the transmission oil cooler was last cleaned and is there a leak on the transmission communication plug causing oil to wick up the harness on extended downhill descents ?

Now a question was this a soft code or a hard code?
Did the light go out be itself either after the descent or when you switched it off and then restarted it or was it permanently illuminated?

If it was soft code why did you clear that stored code and open up all the OBD 2 monitors?
Curious !!:thinking:
Dennis
Mechanic

autostaretx
03-06-2017, 01:14 AM
In the Ord code list, P2091 is an oxygen sensor fault, P2A00 isn't listed,
and P2511 has two possible interpretations:
either:
(a) EGR positioner error (quite likely shorted to ground)
or:
(b) a torque converter lock-up problem, look for overheating as a cause

--dick

talkinghorse43
03-06-2017, 03:33 AM
I've always used engine braking to help come to a stop (or down a long hill), but I keep rpms <~3500. Since cruise control downshifts & uses engine braking to control speed, I've always thought engine braking was meant to be used. No issues to-date.

cahaak
03-06-2017, 04:49 AM
I've used it multiple times coming down some large hills, some with the plain van and others with the camper towed behind it. Never had any issues. I make sure that I get ahead of the curve so that the rpms don't get too high and use the brakes as necessary. I have come down some steep hills in 3rd only. It is much more controlled that using the brakes, kind of like towing a chute behind you.

Chris

talkinghorse43
03-06-2017, 01:33 PM
I've used it multiple times coming down some large hills, some with the plain van and others with the camper towed behind it. Never had any issues. I make sure that I get ahead of the curve so that the rpms don't get too high and use the brakes as necessary. I have come down some steep hills in 3rd only. It is much more controlled that using the brakes, kind of like towing a chute behind you.

Chris

I used 2nd downhill (& some uphills) when towing my son's car (unbraked tow dolly) and carrying most of his household goods (~12k lbs GCVW) from San Fran to Boston. I took precautions as above.
Estimates afterwards were that my van can generate a max of ~70 braking HP.

Aqua Puttana
03-06-2017, 01:47 PM
...

I had stayed well below red line on both cases. ...
What is well below?

Not that you asked...

I avoid using radical downshift and higher RPM engine braking for hills. I prefer to use a high(er) gear and apply my brakes for harder braking, relatively short time periods to help to control my speed as necessary.

I feel it isn't good for the engine to "float" at higher RPM's. ...
I too have used engine braking on many long grades. I have never had any resulting dash warnings or DTC's.

Maybe the OP is a bit too aggressive with the engine braking?

vic

autostaretx
03-06-2017, 05:38 PM
When you tap the shift stick to ask for engine braking, the Sprinter will not drop into a gear that would over-rev the engine.

What i don't know is whether it will UPshift if the subsequent coasting threatens to (or does) take you into the red zone.

(and i have to admit that's not an experiment i'm planning to try...)

--dick

talkinghorse43
03-06-2017, 05:46 PM
What i don't know is whether it will UPshift if the subsequent coasting threatens to (or does) take you into the red zone.

In cruise, it kicks out of cruise (& into 5th), but if you're in control, it won't upshift. IIRC, the last is in the Owner's Manual.

Aqua Puttana
03-06-2017, 05:52 PM
...

What i don't know is whether it will UPshift if the subsequent coasting threatens to (or does) take you into the red zone.

(and i have to admit that's not an experiment i'm planning to try...)

--dick
I do know that while using engine braking on a grade the ECM/ECU/TCM will allow higher no-load revving than I like. I use the brakes to keep things in [what I think is] proper control.

Once in a given gear, I am also not willing to test and see what happens for no-load red line TCM response.

vic

ptheland
03-06-2017, 07:54 PM
What i don't know is whether it will UPshift if the subsequent coasting threatens to (or does) take you into the red zone.

I can't speak to the Sprinter, but I have had other vehicles (all gasoline) that would upshift while coasting downhill when near the RPM red line.

Those make for ... ummm ... interesting situations. Engine braking diminishes quickly, speed increases quickly. Service brakes applied vigorously. :eek:

p3424
03-06-2017, 10:10 PM
In both the E320 and Sprinter, I kept the RPM to about 1000 to 1500 below the red line.

Granted the E320 took a bit more wear and tear coming down from Pikes Peak, CO, which is at 14,000 feet elevation. The p0700 code didn’t occur during the decent, but about half an hour or so after on relatively level road. Also, as I recall, the transmission or engine did seem to be slightly rougher and have just barely perceptibly more vibration then before. I suppose at 120K, maybe mercedes are not quite fully broken in yet as its rarely revved close to redline other than these extenuating circumstances.

Its being over a year and half ago from the time the E320 gave the transmission OBD code. Otherwise its holding up well with just the usual maintenance items its beginning to need, like CV boots and front end bushing, and probably gas cap again for the persistent pending p0442 code.. No other code had occurred since Pikes Peak.

The 2006 Sprinter was on a lesser decent of about 5 to 10 minutes long outside of NYC in CT. Similarly, its about 15 to 20 minutes after being on flat road that the three OBD code P2A00, P2091, P2511 showed up. I might be a bit on the panic side as Dennis pointed out these code could mean a host of major things. But it’s the powertrain code that made me think back to the E320 so I took a chance to clear the code and hope it goes away. So far so good 600 miles later: no code and no pending code.

Thanks for the various inputs about the codes and driving styles. I am still inclined to believe the limits of the mechanical and electrical system on the transmission as programmed is reached when braking with low gear for more than 5 minutes. The same error codes are probably reproducible. Lucky I had OBD reader with me in both cases. I might just have to use the brake pads a bit more from now on to avoid the anxieties from the check engine light…

autostaretx
03-06-2017, 10:26 PM
There have been a number of times i've easily exceeded 5 minutes in engine-braking-downhill.

The most recent was roughly 6 miles of road at 30 to 40 mph dropping down through the switchbacks of the Mackenzie highway (OR 242) just west of Mackenzie pass. 2700 foot drop, tapping up and down between 3rd and 4th (and occasional brakes).

But my Sprinter isn't very heavy (~5500 lbs, loaded), so i'm lower on the heat-dissipation curves.

--dick

talkinghorse43
03-06-2017, 11:24 PM
But my Sprinter isn't very heavy (~5500 lbs, loaded), so i'm lower on the heat-dissipation curves.

If you mean that you expect the tranny to heat up after down shifting to engine brake, my experience has been the opposite as I see both the engine coolant and tranny fluid temps drop on a long downhill. I imagine much of the energy heats the air being pumped by the engine. For mine, the pressure of the air is increased by ~20 psig (exhaust-intake).

Aqua Puttana
03-06-2017, 11:38 PM
Maybe it is a case of operating philosophy.

My use of engine braking is not to save wear and tear on brake parts. Brake part/replacements are cheap. Especially DIY. I use engine braking to allow controlled use of the service brakes and avoid brake fade. I will not sacrifice the drive train to save on brake replacements.

So far I have yet to experience brake fade... and I want to keep it that way.

:2cents: vic

ptheland
03-07-2017, 12:24 AM
My use of engine braking is not to save wear and tear on brake parts. Brake part/replacements are cheap. Especially DIY. I use engine braking to allow controlled use of the service brakes and avoid brake fade.

That's the way I learned to drive. You don't downshift when going down long hills to save wear and tear on the brakes. You do it so that you still HAVE brakes at the bottom of the hill.

It's not as critical in smaller cars, but becomes more important as the weight of the vehicle increases. I don't see 18 wheelers staying in high gears going down hill. They keep in low gears to keep the speed down so they don't have to ride the brakes and heat them up to the point of failure. The same philosophy would apply to highly loaded vehicles of any type - like Sprinter based RVs or conversions. (I could rattle on about exceeding GVWR limits and braking down long hills, but I'd likely wear out my welcome pretty quickly.)

I'm the first to admit that some of the things I learned back in the stone age when I started driving are no longer applicable. But I don't think this is one of them.

owner
03-07-2017, 01:59 AM
Maybe it is a case of operating philosophy.

My use of engine braking is not to save wear and tear on brake parts. Brake part/replacements are cheap. Especially DIY. I use engine braking to allow controlled use of the service brakes and avoid brake fade. I will not sacrifice the drive train to save on brake replacements.

So far I have yet to experience brake fade... and I want to keep it that way.

:2cents: vic

Yep same here. On really long descents, I've gotten into the habit of switching on the AC and blower on full, it provides a noticeable braking effect. It also helps me remember to keep the AC system seals lubricated during winter etc.

King_1223
03-23-2017, 01:36 AM
I had this very problem today. I had a 15 Mile decent at 6%. I used engine braking and about half way down my engine light came on . I drove to the nearest auto part store and had them scan it. Code P2A00 was the only code. Not sure how I should handle this problem. Does anyone know a good sprinter mechanic in Las Vegas?

talkinghorse43
03-23-2017, 02:06 AM
I had this very problem today. I had a 15 Mile decent at 6%. I used engine braking and about half way down my engine light came on . I drove to the nearest auto part store and had them scan it. Code P2A00 was the only code. Not sure how I should handle this problem. Does anyone know a good sprinter mechanic in Las Vegas?

Did your engine shut down on the descent? That happened to me and I found it shut down due to high rail pressure - rail pressure solenoid was sticking and didn't open enough to control rail pressure.

pvsprinter
03-23-2017, 05:50 PM
A few years ago on a long steep grade on a blue highway in Idaho I was following a coach based RV towing a Cherokee. I was in second gear and periodically apply the brakes to stay between 2500 and 3000 rpm with the van loaded to 7K+ pounds (06 2500 conversion). The coach was getting further away and when bottom was reached in a small town, I had turn on the fog lights to see through the smoke from the coach's burning brakes. I agree you down shift so that you have brakes at the bottom.
Bob

King_1223
03-25-2017, 02:15 AM
Did your engine shut down on the descent? That happened to me and I found it shut down due to high rail pressure - rail pressure solenoid was sticking and didn't open enough to control rail pressure.

Nope just engine light. I have had the light cleared and it has not come on again.