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Discussion Starter #1
Car: 2006 Federal Elise with factory 2ZZGE, normally aspirated and stock.

History: Original owner, no accidents, weekend car in garage all its life. Northern Chicago suburbs, winter garage kept. No exposure to weather except some sun! Purchased at Fox Valley Motorcars new. Some background: Elise would also periodically show empty fuel tank when I get in and turn the key to on just prior to pressing the Engine Start button, I realized I would not hear the relay or fuel pump. A few taps around the ECU area would temporarily fix the problem. This was pretty much fixed with a new MFRU (see below).

Symptoms: CEL keeps showing P0638 and car stays in limp mode with P2104.
Observations: While the engine is off, ignition on and CEL is already on - P0638 shows on the scanner.
I noticed that with accelerator pedal at rest : ACC POS D% is 18.8 (with down arrow) and ACC POS E% is 9.4.
With accelerator pedal fully pressed the readings are: ACC POS D% is 79.2 (with down arrow) and ACC POS E% is 39.6.

Question: Is this a problem with the two ACC POS readings D and E not matching?

Below are the things I have tried so far:
New Throttle Body
May 2020
Cleaned Throttle Body connectors May 2020. Comment: Car remains in P0638 and P2104 Forced TAC mode.
New Lotus MFRU (Multi Function Relay Unit) – May 2020. comment: This seemed to help with when starting the car the fuel gauge reads empty and did not hear the fuel pump. Now I hear fuel pump priming and car starts but remains most times in P2104 forced TAC mode.

May 2020 : Cleaned Air Filter and took MAF Sensor out, inspected and cleaned with MAF sensor specific cleaner – no change in behavior after putting it back together.

Persisiting symptoms – Car starts up and reaches operating temps of 165Fahrenheit then goes into P0638 and P2104 limp mode. Cannot always clear out P0638 code via scanner and thus car remains in limp mode. Have disconnected battery and let sit overnight, pressed horn and tapped brakes to rid of residual electricity in the system.

Any help would be most appreciated. Are the accelerator readings between the two accelerator sensors supposed to be as shown above? D is about double what E shows?
Car remains jacked up until I find out whats going on with this car.


Thanks guys.
 

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I found several previous posts and threads on this and this one was the only one that followed thru to resolution. Try this maybe? P0638 P2104 - CEL, Unable to move
 

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Discussion Starter #3
I found several previous posts and threads on this and this one was the only one that followed thru to resolution. Try this maybe? P0638 P2104 - CEL, Unable to move
Yep, that was me posting in the earlier thread which was years ago, the problem has returned but this one focuses in the accelerator pedal, should I have just added to that thread?
 

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Ah ok. I did notice the other two posts that didn't post to resolution were both pointing to ECU flash. Too bad you don't have a spare TB and pedal assembly so you could rule them out. Hopefully someone up on ecu could chime in on your pedal inputs. Given that several have had this problem it will be interesting to hear what final resolution is. Good luck! Richard
 

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Discussion Starter #5
Ah ok. I did notice the other two posts that didn't post to resolution were both pointing to ECU flash. Too bad you don't have a spare TB and pedal assembly so you could rule them out. Hopefully someone up on ecu could chime in on your pedal inputs. Given that several have had this problem it will be interesting to hear what final resolution is. Good luck! Richard
Thanks Richard ( Catsailr27)!

I have a spare TB now (I was able to get a new one for a somewhat decent price), I trust both to be good ones and I'm keeping the new one on the car. I am definitely looking at the accelerator pedal now as a possible culprit, when I first looked at the readings (shown earlier in the first post) I really do expect both D and E accelerator pedal circuits to match but what makes me question if that is the true is that the D % seems to maintain twice the % value found in E. Is it supposed to work that work that way?
I've been searching all earlier posts. Might just order a new accelerator assembly - deciding. Good thing i'm about 5'7" about 160 pounds and can squirm my way down there and look at what needs to be disconnected to get a new assembly in. Having peeked ealier down there I'm not clear how to disconnect the harness from the pedal or even how to get the pedal out. I did read earlier its two bolts but perhaps someone can confirm?

On the fun side - and perhaps just in time to help with this issue - I have a new Lotus Sport ECU coming!
 
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Sounds like you've got everything coming and hopefully will reach resolution soon! I kept my old Koldfire tune ECU as backup and bought another for the Fastworks tune for my REV300 just for PD issues like this. Richard
 
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Sounds like you've got everything coming and hopefully will reach resolution soon! I kept my old Koldfire tune ECU as backup and bought another for the Fastworks tune for my REV300 just for PD issues like this. Richard
I just took another peek at the DBW accelerator pedal assembly, I see that there are two bolts up front which appears easy enough to access and one bolt buried way in the back. I can feel the rear bolt head with my finger but sure feels like a tight fit. I have not seen one thread that details the removal of this DBW accelerator pedal assembly from the car but seems like there is no other way to get at it except from underneath laying upside down in the driver's footwell.

I am also not clear exactly how to disconnect the connectors from the assembly.

edit: I should also add, I heard my back crack a little while laying upside down in the Elise and looking up at the bolts holding the acc pedal assembly to the car. Its been a nagging problem but now my back feels a little better after I wiggled myself out. :)
 

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Your pedal is fine, and both of those codes point to the throttle or throttle control circuit, not the pedal. The throttle should have two opposite feedback circuits so they always add to be a constant voltage, so you can always splice in and measure those.

The pedal has one 100% and one 50% circuit, so you can see in your data that one is always twice the other, so that's fine.
 

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Discussion Starter #9
Your pedal is fine, and both of those codes point to the throttle or throttle control circuit, not the pedal. The throttle should have two opposite feedback circuits so they always add to be a constant voltage, so you can always splice in and measure those.

The pedal has one 100% and one 50% circuit, so you can see in your data that one is always twice the other, so that's fine.
Thanks cyow5 for the info. One more question - there are times I see that ACC POS D % displayed is not exactly twice that of E, if I have the ignition on, engine not running and I slowly step on the pedal more and more until full throttle I can see that in certain positions ACC POS D can be .2 or .1 off. Should I ever see that ? I'm going to try again and post some pics up here of the two sensor circuits % readings on my scanner.

ok, so with the above I'm thinking of the throttle body - which is new from toyota and gives me the same code as the original. I am tempted to check the wire loom leading from the Throttle body connector.
 

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Thanks cyow5 for the info. One more question - there are times I see that ACC POS D % displayed is not exactly twice that of E, if I have the ignition on, engine not running and I slowly step on the pedal more and more until full throttle I can see that in certain positions ACC POS D can be .2 or .1 off. Should I ever see that ? I'm going to try again and post some pics up here of the two sensor circuits % readings on my scanner.

ok, so with the above I'm thinking of the throttle body - which is new from toyota and gives me the same code as the original. I am tempted to check the wire loom leading from the Throttle body connector.

I mean, both those codes are actuator-specific, so the car doesn't seem to be bothered by anything it is seeing from the pedal side. That pretty much leaves the wiring and ECU power stage. Thankfully, none of the DBW stuff is digital outside of the ECU so you can do a lot more testing than "try and see".
 

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Discussion Starter #11
ok cyow5 thank you, so now I am focusing on the wires leading from the ECU to the Throttle Body.

I've already disconnected both ECU side of the harness and the Throttle Body side.

Perhaps I can use my multimeter and check for continuity in the TB circuit wires but I'm having some difficulty finding a pinout diagram for the '06 DBW ECU which can show me the exact ECU wire to check. Please can someone point me to it? I tried searching last night but its elusive for me. I am suspicious now if the Throttle body is getting 5v from the ECU.

I am no mechanic or car technician guys so please bear with me if I seem overcautious or hesitant to start poking a multimeter lead into just any wire.
 

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It's hard to make out the pin names, but the colors should help. And no worries, proceed as slowly and carefully as you need to!

1263934



1263935
 

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You can also check the ground to 5V resistance as well as the TPS1 and TPS2 to ground resistance with the harness unplugged. You should be able to move the throttle by hand and see the TPS1 and TPS2 resistances change.
 

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Cool! Thanks cyow5! Very useful diagrams. I checked both Throttle bodies - first checked the one off the car - easier and get the hang for what I was checking for ....and then checked the one on the car, both checks out ok.

Ok, now I'm trying to find a pinouts diagram for my '06 ECU DBW since I also want to confirm that the wires leading to the throttle body has continuity from the ECU. I saw a pinout diagram online from HASSTURBO.COM but the pins don't seem to match what I see on my harness. My ECU says "A121E0009F"

Side note: If it makes a difference my '06 DBW Elise has a white dash- I read in one of the threads there's a difference between white and black dash cars and their ECUs? This is news to me.
 

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Discussion Starter #15 (Edited)
So after looking at the diagrams above and checking the boefab.com site I see that the TB diagram above includes the engine ecu (engine side) pinouts, answer was right in front of me the whole time. haha!
ok so for readability (for anyone else with same problem reading this) the ecu side pinouts are RL1(M+), RL2(M-), RD1(GND), RE3(TPS2), RM4(5V), RD3(TPS1) for the Throttle Body diagram provided above.

I'm too tired to check out those wires tonight for continuity, will check it tomorrow for sure.
 

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So after looking at the diagrams above and checking the boefab.com site I see that the TB diagram above includes the engine ecu (engine side) pinouts, answer was right in front of me the whole time. haha!
ok so for readability (for anyone else with same problem reading this) the ecu side pinouts are RL1(M+), RL2(M-), RD1(GND), RE3(TPS2), RM4(5V), RD3(TPS1) for the Throttle Body diagram provided above.

I'm too tired to check out those wires tonight for continuity, will check it tomorrow for sure.
Since P2104 is just a consequence of P0638, see what happens when apply battery voltage directly to the M+ and M-. It should go WOT and then 0° if you reverse the wires. Try this with the wires connected to the TB but disconnected from the ECU then apply voltage at the ECU connector-side. This should confirm if the problem is inside or outside of the ECU.
 

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Since P2104 is just a consequence of P0638, see what happens when apply battery voltage directly to the M+ and M-. It should go WOT and then 0° if you reverse the wires. Try this with the wires connected to the TB but disconnected from the ECU then apply voltage at the ECU connector-side. This should confirm if the problem is inside or outside of the ECU.
12V is ok? I would assume it is.
 

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have you ever installed a data system that was measuring the 5V off the pedal or TB? when my wiring wasnt great I was getting errors like these after installing those sensors poorly. I would check the crimps and harness at each of the plugs at the TB and pedal I think.
 

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Discussion Starter #19
ok my TB checked out ok after putting battery voltage to M+ and M-. It went WOT and 0 when applied and then reversed.
 

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have you ever installed a data system that was measuring the 5V off the pedal or TB? when my wiring wasnt great I was getting errors like these after installing those sensors poorly. I would check the crimps and harness at each of the plugs at the TB and pedal I think.

ok, so I have the ECU off after carefully disconnecting the harness. I was hoping that looking at the inside of the ecu connectors I would see some clear markings where to find the pinouts for RL1(M+), RL2(M-), RD1(GND), RE3(TPS2), RM4(5V), RD3(TPS1) for the Throttle Body, this way I can find the corresponding wires and check both sides of those wires for continuity. I cannot see /find them. All I see are letters on the bottom on the ECU from A to M. :(
 
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