AlSIN AS69RC shift position sensor

[mpaulson]

Looking for one of the tech's out here who may know if this sensor is an external part to change on this transmission. I'm 600 Km's from the nearest dealer and on holidays and Chryslers road side assistance has authorized a local shop to check the codes and contact them back to see what can be done. I have to wait till Wednesday since Tuesday is a holiday here in Canada. One code was P 0706 and the other was the shift position sensor. I've had the shift position code three times now and shutting the truck off and restarting it usually makes it go back to normal and get out of limp mode, but not today. Just had it at the dealer last week for this and they did the series of test that is called for and it checked out good. Of course it did. It seems that the three times it has acted up is after towing for a long time. I'm thinking that heat soak may have something to do with it. Is this an easy part to swap? I hope it's not in e valve body or something. Once the truck cooled a bit today it was fine till I went to put it in reverse then it showed up again. I'm betting that tomorrow morning it will be fine again,but if not I've got to get this thing fixed.

 

[transe]

Yes, the Aisin trans uses an external Trans Range Sensor (TRS), which is on the driver's side of the trans, near the rear of the case, just above the oil pan. Just follow the shifter cable and you'll find it.

But before they replace the TRS, have them simply disconnect the wiring harness from the TRS and inspect the pins for any obvious problems (bent pins, pins pushed partway out, corrosion, etc.). In addition, there is a 34-pin inline wiring connector (behind either the right front or left front wheelwell) that I have seen issues with on some trucks. The TRS circuits go through that connector (on their way to the TCM), so I would also check that connector out (before replacing the TRS).

 

[mpaulson]

Well, 600km's out of my way on holidays to the nearest dealer, they check the connectors and changed the transfer range sensor, and three hours later and 250 Km's away from there it did it again! Went into limp mode and it got P0850 again, neutral/park circuit. Anyone have any ideas as to where to go from here? Bad wiring that shows up with hours of use? Bad TCM that shows up with time? This has occurred five times now at least and the one constant seems to be time, at minimum three hours and towing. Trans temp has stayed between 70 and 80 degrees Celsius, totally normal.

 

[transe]

I believe P0850 is an ENGINE fault (not a trans fault), and basically means (I think) that the ECM thought the trans was in Park / Neutral while you were driving down the road. So I think it's more of a communication problem between TCM and ECM, than a Trans Range Sensor problem. Let me research it a little more (I'm in a training class today) and I will post further details...

 

[JLandry]

From the PCM (Powertrain Control Module) diagnostics section of the 2014 Factory Service Manual:

P0850-PARK/NEUTRAL SWITCH PERFORMANCE

Theory of Operation

The transmission PRNDL diagnostics will detect transmission stuck in park error, if the vehicle speed is greater than a calibrated threshold and selected gear is PARK according to the received CAN message. It will also detect transmission stuck in drive error, if the engine crank state is seen while the selected gear is DRIVE according to the received CAN message.

• When Monitored: When the vehicle is moving.
• Set Condition: Vehicle speed is detected while the transmission reports that the vehicle is in park.

Possible Causes

TRANSMISSION STUCK IN PARK

TOWING VEHICLE WITH THE IGNITION ON​

Always perform the Pre-Diagnostic Troubleshooting procedure before proceeding. (Refer to 28 - DTC-Based Diagnostics/MODULE, Powertrain Control (PCM) - Standard Procedure).

Repair

TRANSMISSION STUCK IN PARK

• Repair the transmission/CAN related problem.

 

[mpaulson]

Is there a pin in the transmission that pushes on the range sensor that could be sticking, not sliding back in thus telling the range sensor that it is in park? "Repair the transmission/CAN related problem" Something like a pin that slides in and out that is stuck in the out position or something that with a good heat soak could cause it to be "sticky"?

 

[transe]

Is there a pin in the transmission that pushes on the range sensor that could be sticking, not sliding back in thus telling the range sensor that it is in park? "Repair the transmission/CAN related problem" Something like a pin that slides in and out that is stuck in the out position or something that with a good heat soak could cause it to be "sticky"?

The brief answer is, no. The TRS operates via the rotating shaft that is actuated by the shift lever. So I don't think there's any way for it to be "stuck."

 

[MCrossley]

obvious question but if it is a rotating encoder is the indicator in the dash showing the appropriate position all of the time or are you seeing it off by one at any given time?

 

[mpaulson]

obvious question but if it is a rotating encoder is the indicator in the dash showing the appropriate position all of the time or are you seeing it off by one at any given time?

It does show the correct gear, but once in limp mode the PRND are yellow and it doesn't show what gear you are in. Operates totally normal till you go to change gears then it happens. Just did it again this afternoon when I got to today's destination after 4 hours driving.

 

[transe]

OK, let's think about this logically.

There are five (5) TRS circuits. One of those (the T41 circuit) goes directly from the TRS to the PCM; the others go to the TCM. I'm guessing that the T41 circuit is the "neutral safety" signal, that would be grounded (I'm guessing) in Park or Neutral. The P0706 fault means the TCM saw an "invalid" TRS code, that is, a combination of switch states (on its four circuits) that should never exist (that doesn't correspond to any valid gear position). When the TRS code is invalid, the TCM calls for the PRNDL display to be either blank (nothing highlighted) or "all" (meaning ALL the PRNDL positions are highlighted). I'm not sure which one ("blank" or "all") the Aisin trans uses. The P0850 fault means the PCM received a CAN bus message showing trans in Park (when vehicle was actually moving at greater than some threshold speed), or trans in Drive while the engine was being cranked. So P0850 relates only to a CAN bus message (not the state of the T41 circuit that the PCM is monitoring). The CAN bus message for trans PRNDL position must originate from the TCM.

• So the P0850 fault could be set if you throw the trans into Park while driving down the road, but that would not set a P0706 (or blank out / light up all the PRNDL positions). And I'm assuming you didn't actually shift it to Park while moving.

• A bad TRS (or bad wire) that caused an invalid PRNDL code (and P0706 fault) should not cause a P0850 fault, since it would not cause the TCM to send a CAN bus message for Park or Drive (at an inappropriate time).

• If the T41 circuit is the "neutral safety" circuit, then it would be possible (if T41 were grounded all the time, let's say) to set the P0850 fault, if you actually did crank the engine while the shifter was in Drive. But again, that would not set a P0706 fault, and I'm assuming you didn't actually do that.

• Since P0850 requires a VALID TRS code (so the TCM is communicating either Park or Drive over the CAN bus), while P0706 requires an INVALID TRS code, I don't think both codes can be set simultaneously. But apparently your problem is causing an invalid TRS code (and hence, P0706) at some times, and an incorrect Park (or Drive) indication (and hence, P0850) at other times.

• Let's call the four TRS circuits that connect to the TCM A, B, C, and D. (In actuality, A is the T42 circuit, B is the T3 circuit, C is the T1 circuit, and D is the T4 circuit). In Park, A and D are "active" (which I'll assume means they are grounded). In Drive, B and C are active. So I don't think there's any single circuit failure that would give you a false "Park" reading while you were driving down the road. However, Neutral has B and D active, and in the transition zone between Neutral and Drive, B, C, and D are all active.

• So I'm wondering if perhaps your C circuit is "active" (grounded?) when it shouldn't be. If C is active in Park or Reverse, that would give you an invalid TRS code (and thus, P0706). If C is active in Neutral, the TCM will think the shifter is in between Neutral and Drive. I'm guessing that the TCM might send a CAN message for "Drive" in this case (if the TCM thinks the shifter is in between N and D, it is safer to tell you it's in D, than to display N when you might actually be engaging Drive). So, if the shifter is actually in Neutral, the T41 circuit would tell the PCM that it's OK to crank. But the TCM will be seeing "transition zone between N and D", and may therefore be broadcasting "Drive" over the CAN bus. If so (and you start the engine in Neutral), that would explain the P0850 fault. So, do you ever start your engine in Neutral (rather than in Park)? When you get the "all yellow" PRNDL display, is that when you're in Park or Reverse? If you shift back to Neutral or Drive, does the PRNDL display then read properly? That would support the "bad C circuit" theory.

As you can see, there's a whole lot of "guessing" on my part here. But I think this offers one feasible explanation. The "C" TRS circuit is known as the T1 circuit in wiring diagrams, and goes from pin 1 on the TRS to pin 10 on the TCM. It also goes through a wiring connector behind one of the front wheelwells (at pin 16). The problem could be a bad TRS itself, or could be a wiring problem (bad connection, corrosion, etc.). I would check the wiring connections over visually (especially the connector behind the wheelwell) before replacing the TRS.

 

[mpaulson]

Thanks Transengineer,
The TRS was replaced on Monday, didn't help. I definitely have the truck in park, at least physically, every time it is shut off and started. I could tell that the tech didn't touch the connector under the drivers wheel well because it is still caked in the mud from the gravel hi way that I traveled before they saw it. It has got to be something that it time/heat related because it never does it unless it's been driven for at least three/ four hours steady. Is the TCM on this truck mounted on the firewall above the turbo like it was on my 07.5? Could it be a possible heat soak culprit? Yesterday I had this nightmare thought that the two screws that I put in the floor where the old dimmer switches used to be to mount my train horn switch my have hit the wire harness under the floor. I tried looking up there from the underside, but would have to remove the wheel well liner in order to see to. I removed the two screws just in case, but it still happened yesterday after this. So they obviously were not grounding out anything. This is really going to be a painfully process to go through with he dealer because it never does it until after the three or four hour minimum driving time which means that I will only ever find out if what they did worked on my next camping trip! Good way to start a camping trip. I wonder if Chrysler has any history on such a case yet for them to reference?
When I get the all yellow indicators, they stay that way and don't show what gear you are in. I am usually going from park to drive or reverse but yesterday I was going from drive to park when it did it and I was for sure at a complete stop. The first two times this happened I could shut the truck off and immediately restart it and things were normal but the last five times now I have to wait for at least 15-20 minutes, then it will be normal when I restart.(something has cooled down enough?) Is it possible that the unit that sends the signal for the speedometer is some how sending a signal that the wheels are turning at such a small amount that it isn't noticeable on the speedometer? Could it be having a heat soak issue? Thus making the truck think it's still moving when I'm shifting?

 

[transe]

Your idea about it being heat-related makes sense. Your TCM is actually inside the cab, underneath the dash, just to the left of the steering column.

You might try simply cleaning off, disconnecting, cleaning, and reconnecting the wheelwell connector.

When you have the problem, does the trans still operate normally? I know on the 68RFEs, the trans will still function fine, even with an active TRS error (P0706). You just won't have any valid PRND indication. So hopefully, you're not stuck on the side of the road when this happens.

 

[mpaulson]

If the TCM is in the cab then my external heat soak idea doesn't fit, at least not for the TCM itself unless it is internally producing more heat than it should.
The transmission operates normal once it comes out of limp mode. The first two times it did it it was simply a shut the truck off and restart it and it went back to normal with the code and engine light of course. The last 5-7 times it has required about 15-20 minutes of shut down time and then it comes out of limp mode. So whatever the culprit is, it stays active for that bit of time before it reverts back to normal to allow it to come out of limp mode. I haven't been stranded by this yet, I just don't take it out of drive when I've been on the road for a long time unless I know that we will be stopped for at least 15 minutes. I stopped on the highway to take a picture of a bear yesterday and left it in drive and put the parking brake on instead because I didn't want to take a chance and be on the shoulder of the road in limp mode. Once it's out of limp mode everything is normal, operating, indicators etc.

 

[transe]

Hmmm.... I wouldn't think a P0706 fault would put you into limp in (although I could be wrong, on the Aisin). You have no other fault codes (besides P0706 and P0850)?

 

[mpaulson]

Hmmm.... I wouldn't think a P0706 fault would put you into limp in (although I could be wrong, on the Aisin). You have no other fault codes (besides P0706 and P0850)?

It has always had the P0850 each time, the P0706 has not been there everytime. So from your statement the P0850 is the limp mode causer.

 

[mpaulson]

Just went and checked the last set of codes and it is P0850, P0706 and U110E(no definition)

 

[rrl989]

I had an intermittent electrical EVIC/dashboard issue. Took 4 dealers visits over 4 months before they fixed fit (and took my initial advice!). I suggest you make short video of the issue for the Ram Engineers to view. I posted mine on Youtube and gave the dealer the link. Tell them the get 3 more attempts, JMHO - don't fool around with electrical intermittent issues. Good luck.

 

[Bob V]

When I googled that code it came back a line pressure also. Have you checks your fluid when it acts up. Maybe the oil foaming from an overfill or the pump sucking air?

 

[transe]

P0850 is an ENGINE-side (PCM) fault, not a trans (TCM) fault, so it should not put you in limp-in. P0850 is Park/Neutral Switch Performance. It does not relate to line pressure.

U110E is Lost Ambient Temperature Message, and involves the ambient temp sensor in the driver's door mirror. So that should not affect the trans, either.

I'm trying to dig into this a little deeper, and get some more information for you. Have you checked the wiring connector behind the wheelwell yet?

 

[transe]

Just confirmed that the P0706 fault WILL put you in limp-in (5th gear, if it happens at speed, 3rd gear otherwise). So it looks like I was wrong about that. Need to check the wiring for the TRS circuits (and first place I would look is that wheelwell connector).