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Old 05-22-2018, 02:39 PM   #1
amayer3
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2002 L-Series 3.0L Sedan
Default 2002 L300 Limp Mode

Hey,
This is my first time here, I've found many answers on this site but this problem continues to puzzle me. Let me start by giving a little history for the car. It was originally my dad's, where he maintained it and it ran fine, then he gave it to my brother, who still took care of it but it's where issues (like limp mode) started happening. He has replaced the MAF Sensor, the BCM, the thermostat, had the transmission fluid changed. Eventually the car wouldn't start after running for a while, that's when he stopped driving it. Then last summer he told me if I could fix it I could have it. I talked to my friend's dad who is a mechanic and we replaced the crankshaft sensor, and that fixed the starting issues.

The limp mode (the service light comes on while driving and it starts to shift hard) continued, but I lived with it (while looking for an answer) much like my brother did. However, recently it has gotten a lot worse. Now if it has been running for 10 minutes or so, then I turn the engine off and try to start it again it starts, the light comes immediately on and it won't let me shift for a good 15 seconds, then when I am able to shift the engine won't go over 900 rpm (and it limps in short bursts). I have replaced the TCM to fix this, but I don't know where to go from here.

Codes:
P1780
Manufacturer Controlled Transmission
U1206
Manufacturer Specific DCT

Thanks for everyone's help!

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Old 05-22-2018, 03:34 PM   #2
Russet
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2003 L-Series 3.0L Sedan
2002 L-Series 3.0L Sedan
Default Re: 2002 L300 Limp Mode

Has the Tranx been looked at before by a Tranx shop? Also when was the fluid last changed or checked? Also just changing parts will not find you a solution it could make it harder to diagnosis where the problem is coming from.

here's my example when I got limp mode changing the CPS and clearing the codes fixed the problem. Also proceeding this along came the slamshift 1-2 which was a shift solenoid going bad. Once that was fixed no more slamshift. But what you need to do is check your Tranx fluid and level or have a shop do that to verify that is ok first.

Last edited by Russet; 05-22-2018 at 03:36 PM.. Reason: revise

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Old 05-22-2018, 03:59 PM   #3
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2003 L-Series 3.0L Sedan
Default Re: 2002 L300 Limp Mode

From the service manual;

P1780 Torque Reduction Signal - DTC P1780 sets if the TCM receives an invalid torque reduction signal from the ECM.The TCM will inhibit adaptive learning and default to maximum line pressure.

Limp mode or as service and owner's manuals describe it as Reduced Power Mode, is about three things - electronic pedal, electric throttle and ecm. Wiring and/or parts are faulty. There should be an error code, DTC1510, 1511 or 1516 - If DTC P15nn is set, the ECM will default to one of the 2 limp home modes, random injector disable with the engine speed limited to 1800 RPM. The REDUCED POWER telltale will be illuminated and the ECM will remain in this condition for the entire ignition cycle even if the fault is corrected.

There may be several issues here. One is definitely about reduced power mode since you see the RPM indicator/can't accelerate and possibly a xmission pressure solenoid issue. It's a tough situation to be in as this may be overwhelming for any diyer to diagnose and repair. In my opinion, the reduced power mode should be addressed first since the engine powers the xmission. If the engine can't run right then the xmission can't run right.

You could force a reset with battery disconnect and see which errors reappear. Have a reader nearby to decode stored errors.

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Old 05-23-2018, 12:46 PM   #4
floridasl22002
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2003 L-Series 3.0L Sedan
2002 SL2
Default Re: 2002 L300 Limp Mode

Here's my 5 cents....

There are OBD codes and OBD codes. Most can be read by the regular Code Readers. Some OBD codes are specific to each manufacturer and can only be accessed with readers that can read that manufacturers specific codes.

Case in point are TRANSMISSION codes. They can only be read on a Tech11 scanner that can read the GM specific codes, especially transmission issues.

My son has an 03 L300 V6, which has been throwing the wrench light for a good while. It was also starting to do hard shifts on both forward and reverse gears. We took it to an auto trans shop who hooked it up to their Tech11 and told us that the tranny was keeping pressure high and that was causing the hard shifting. His initial advice was that the tranny needed a rebuild at 130K BUT if we chose not to do anything about it, the tranny could carry on like this until it went into limp mode and that's the tranny saying 'I need fixing".

Having done some more research on this via Google and this Forum, there are others with L series that have similar issues. The root cause seems to be solenoids in need of replacement.

The cost of the solenoids is not unduly expensive as replacing the pressure solenoid and the 1-2 and 3-4 solenoids are going to hit you less than $150.00. It's getting to them that is the bugbear as they are located down the side of the tranny on the drivers side.

There is a thread on here somewhere detailing the job, but very basically you have to lower the tranny, remove the drivers side driveshaft, brake, etc to get access to the side pan. Once removed, it's a straight forward plug and play removing and replacing. One guy who did that job spent a whole weekend doing it and said he would never do the job again BUT replacing the solenoids fixed it for him.

If I want to fix it for my son's L300, then I am staring at the same job.

I would also suggest that you check the tranny fluid level/condition as well. Sometimes issues can be fixed by simply replacing the fluid & filter if they haven't been done forever. Once again, Saturn conspired against the L series owner by NOT installing a tranny dipstick in the car. You have limited ways of checking the level, but you need to car off the ground on all 4's to be able to do it. If you know someone with a 2 or 4 post lift, then you can check it. There is a drain/check fill bolt on the side of the tranny. It is like the diff plug on a back axle. You remove it and the fluid is at the correct level when it begins to trickle out BUT the fluid has to be at normal temps first to do this. It is not the safest of jobs to perform with hot oil.

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Old 05-26-2018, 03:51 PM   #5
amayer3
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2002 L-Series 3.0L Sedan
Default Re: 2002 L300 Limp Mode

Hey,
Thanks again for everyone's input, it was all really helpful.
I talked to my brother in law (after I got some ideas as to what was causing it), who is good with cars and he said it was probably the pressure control solenoid he would help me replace it. We started last night and stopped when we could take the transmission side pan off, so we could finish it today. When we went back at it today we noticed a lot of rust in the frame and decided that it was not worth fixing any more.

I just wanted to put the resources out that I found and we used in case someone else has the same issues, so they know what to do! I hope this helps. The forum won't actually allow me to post hyperlinks so just as the www

This is the Control Pressure Solenoid:
rockauto.
com/en/catalog/saturn,2002,l+sedan,3.0l+v6,1388482,transmission-automatic,pressure+control+(epc)+solenoid,17897

Here are some links to instructions that I found on other threads:

This one is a very helpful step by step instruction:
saturnfans.
com/forums/showthread.php?t=152205

This one has what the link above did (with more details and helpful tidbits) in the third post of the thread (and some pictures for reference):
saturnfans.
com/forums/showthread.php?t=231685


But yeah, moral of the story, this car was a beast to work on, and in my experience with it, nothing was done or fixed easily. However, this was an amazing 1st car for me, the gas mileage was excellent, it drove well, I learned a lot about cars in general and I will always love Saturns.

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