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rotimy 09-27-2017 08:00 AM

Limp mode when I accelerate or use air codition
 
Please I need your help.
I have a saturn L300, 2001 model v6, 3.0L
Whenever I use the air condition or drive the car for about 3miles, the car gets into limp mode. If I dtive above 40mph or try to speed up while climbing an hill, it also gets into limp mode. If I stop the car and restart the car after minutes of waiting, it will drive well provided I didn't put on the air condition or go above 40mph.
I was advised to change the throttle body. I bought a fairly used throttle body as replacement but the problem parsists. A mechanic after troubleshooting on the car adviced me to change the ECM. I have ordered for ECM but I am not sure this will solve the problem. Please do you have any advice for me?

Claybury 09-27-2017 08:38 AM

Re: Limp mode when I accelerate or use air codition
 
Change your mechanic, then get a scanner with live data and monitor all sensor outputs to see if one is giving questionable readings. I would start with the O2 sensors.
If the check engine light is on please post the codes that were set.

pierrot 09-27-2017 09:59 AM

Re: Limp mode when I accelerate or use air codition
 
[FONT="Palatino Linotype"][SIZE="3"]Welcome to SaturnFans, [B][I][COLOR="blue"]rotimy[/COLOR][/I][/B]!

[QUOTE=rotimy;2255528]I have a saturn L300, 2001 model v6, 3.0L.
Whenever I use the air condition or drive the car for about 3miles, the car gets into limp mode. If I dtive above 40mph or try to speed up while climbing an hill, it also gets into limp mode. If I stop the car and restart the car after minutes of waiting, it will drive well provided I didn't put on the air condition or go above 40mph.[/QUOTE]

1) How long has this problem persisted?
2) What is the mileage and maintenance history of this car?
3) Is the [B][U][COLOR="blud"]S[/COLOR][/U][/B]ervice [B][U][COLOR="blud"]E[/COLOR][/U][/B]ngine [B][U][COLOR="blud"]S[/COLOR][/U][/B]oon (SES) warning light on, or has it been recently illuminated at the dash console?

[QUOTE=rotimy;2255528]
I was advised to change the throttle body. I bought a fairly used throttle body as replacement but the problem parsists. A mechanic after troubleshooting on the car adviced me to change the ECM.[/QUOTE]

4) Was the advice previously received about replacing the throttle body given by the same mechanic who has suggested replacing the ECM?
5) Did this mechanic tell you whether or not there were any trouble codes present to be read from the ECM (typically read as "P" followed by four numbers: P----)?
6) Do you have any background in automotive repair as a DIYer (do-it-yourself-er) or in any other capacity?

Limp mode is a fail safe setting in the ECM related to the "Drive By Wire" accelerator pedal and throttle body. It prevents a "runaway" situation where the driver is no longer able to control acceleration. However, this particular condition may arise from other problems.

[QUOTE=rotimy;2255528]
I have ordered for ECM but I am not sure this will solve the problem. Please do you have any advice for me?[/QUOTE]

[COLOR="green"]If you've ordered a new ECM please don't install it[/COLOR] [B][I][COLOR="blud"]until there has been further investigation into this problem[/COLOR][/I][/B]. As an outsider looking in on this concern, I want and need more information ([I]the reason for the questions above[/I]) before agreeing that replacing the ECM is a proper course of action. It may, or may not correct this condition. If it is [B][U]not[/U][/B] the source of this condition and the part container is unopened, then it may be possible to return it later and receive a refund. Otherwise, you may be stuck with an expensive unneeded new part.[/SIZE][/FONT]

rotimy 09-27-2017 08:45 PM

Re: Limp mode when I accelerate or use air codition
 
[B]Thank you all[/B]

These are the answers I have for now, please I will appreciate more questions and advise.

1. I have been managing this problem for two months.
2. The millage is 114,000+
3. The service engine light has been on befor the problem started, two different mechanics cleared the code but it kept coming back.
4. It was the same mechanic, he first searched for a used trottle body and couldn't get, then later he told me that the current from the ECM to trottle body is inadequate.
He advised me not to change the trottle body until I get right current from the ECM, so he advised me to get ECM.
5. I will call the mechanic tomorrow to request for the codes.
6. Yes, I have little experience, but not so much.

rotimy 09-27-2017 08:47 PM

Re: Limp mode when I accelerate or use air codition
 
There was a time code 1780 kept coming back after the code has been cleared. I will get other codes and post it here.

pierrot 09-28-2017 12:45 AM

Re: Limp mode when I accelerate or use air codition
 
[QUOTE=rotimy;2255612]There was a time code 1780 kept coming back after the code has been cleared...[/QUOTE][FONT="Palatino Linotype"][SIZE="3"]The letter prefix is important as there are four of them: B, C, P, and U. This should be a P (powertrain) code - P1780. If so, my 2000 L-Series L81 (V6) engine manual defines it as "[B][COLOR="blud"]TCM REQUESTED MIL[/COLOR][/B] (malfunction indicator lamp) [B][COLOR="blud"]ILLUMINATION[/COLOR][/B]." It doesn't relate to a specific transmission sensor, merely that the transmission's computer found a problem and sent a message to the ECM to turn on that lamp at the dash console. It does suggest that a problem exists, but that's all one could say with the information available now. The fact that the code returns after it has been cleared means that the transmission's computer has found an issue needing correction.

While I'm a bit uneasy with what your mechanic is suggesting that you do to correct the driveability problem, I have no argument against it. If he is willing to back up his work with a guarrantee then it suggests that he believes his diagnosis is good and is willing to back it up. Since you're probably not familiar with this level of electronic repair on your car then you need to allow someone whom you trust to work on it.[/SIZE][/FONT]

rotimy 09-28-2017 07:38 AM

Re: Limp mode when I accelerate or use air codition
 
I appreciate your response. I called the mechanic this morningg, he told me that the power from the ECM is low and whenever the car is hot, the power supplied is lower. He is 80% sure that the ECM is the problem but not sure if theire are other problems. I plan to fix the ECM myself. I ordered for a plug and play ECM with my car vin number.

Claybury 09-28-2017 11:13 AM

Re: Limp mode when I accelerate or use air codition
 
I hope the ECM fixes your problems. Many bad ECM diagnosis are actually poor grounding issues.
I don't know how your mechanic measured the throttle body power. The throttle motor is driven in current mode by a bidirectional push/pull amplifier. Voltage measurements are largely irrelevant and specialized equipment and a break out harness are required to make the current measurements. Also ECM's don't "put out power", normally the circuits are all sinking power to ground. Power comes from the DC buss voltage. Looking for voltage on the ECM pins is pointless except to see in the power is getting to the ECM.
If the Throttle body or ECM were the problem you should have had P0121, P0221, and possibly a P02135 code. These would mean the throttle is not responding properly to the computers requested position.
An other part of the throttle system is the accelerator pedal position sensor. It is easy to test these parts if you look at live data from the APPS and TPS sensors while slowly depressing the pedal. They should go up and down hand in hand.
The big clue you have is the problem happens when the A/C is turned on. If it were me I would watch the DC buss voltage at the fuse box connections and see what it is dropping to with the car running and when the A/C is turned on. If it is dropping excessively check the cables, ground, battery, battery terminals, and alternator.
Next thing would be to check the engine load live data to see if the the A/C is putting an excessive load on the engine.
After that check the O2 sensor data and the MAF sensor data.
The MAF sensors on these cars are problematic. They will feed bad data to the ECM long before they will throw a code. This can make the ECM think the throttle is open far enough when it is not. It should be reading between 3 to 7 grams/second at idle and increase smoothly as the throttle opens.
The MAF is easily damaged by water. The L series intake is susceptible to ingesting water into the air cleaner box if you drive through a puddle or heavy rain, or a car wash. They even put drain holes in three of the boxes four corners.
One other thing is the 3.0's do not like ethanol. The factory put out TSB's basically saying there will be drivability problems if you put over 10% in the tank. The engine and it's controls were developed prior to the European ethanol directives. It's an Opel engine built in England BTW.

Claybury 09-28-2017 11:20 AM

Re: Limp mode when I accelerate or use air codition
 
A quick way to test the MAF if you don't have live data is to disconnect the MAF harness. The engine will probably start harder then normal and idle rough for a while, until it learns to run off of the MAP sensor alone. You will get a code thrown and the mileage will go down. If it drives better this way you are on to something.
Don't get a junkyard MAF. It may be why the car ended up in the junkyard. A new one will run you $100 or so.

rotimy 09-28-2017 01:31 PM

Re: Limp mode when I accelerate or use air codition
 
The codes are p0731, p0733,p0742,p1748

fdryer 09-28-2017 04:24 PM

Re: Limp mode when I accelerate or use air codition
 
Did anyone measure battery/alternator voltages? Standby battery voltage should be around 12.5v. Engine idling alternator output should be between 13.3v - 14.9v, averaging around 14.5v.

Claybury 09-28-2017 04:47 PM

Re: Limp mode when I accelerate or use air codition
 
Those are transmission codes.
It still could be MAF related as bad MAF data confuses the living hell out of the tranny computer on these cars.
Since the MAF is simple and cheap I would check it out first.
Did you ever experience any slam or hard shifting?

Check the transmission oil level. There is a plug on the side of the case you remove while the car is level and running.
Two codes are saying the transmission is checking the vehicle speed against the engine rpm, looking to see what gear it is in and the numbers don't add up. The tranny thinks it is slipping. It then waves a flag and tells the ECM to turn on the malfunction light.
One code is saying the torque converter clutch is not working.
One says the line pressure solenoid has failed.
If the MAF is good. I would suspect, in this order:
Bad pressure control solenoid
Failing torque converter
Failing transmission pump.

A bad speed sensor could cause the P0731 and P0733 codes, but I don't think they would set a P1748

This is all predicated on the DC buss voltage being good. Low buss voltage can cause all kinds of spurious codes and send you tracking ghosts. It is also predicated on the transmission fluid hasn't been in there for 100K miles. That the filter has been changed at some point. That the tranny fluid level is not low.

The line pressure solenoid can be replaced with the transmission in the car. It is not unusual for them to fail.

fdryer 09-28-2017 05:30 PM

Re: Limp mode when I accelerate or use air codition
 
A minute to measure voltages won't hurt. The car can't run correctly if voltages aren't correct.

Claybury 09-28-2017 05:34 PM

Re: Limp mode when I accelerate or use air codition
 
[QUOTE=fdryer;2255717]A minute to measure voltages won't hurt. The car can't run correctly if voltages aren't correct.[/QUOTE]

Covered in post #8.

fdryer 09-28-2017 05:36 PM

Re: Limp mode when I accelerate or use air codition
 
All well and good but no reply from the OP on whether or not voltage checks were made. Covering the basics goes a long way to avoiding replacing unnecessary parts if it turns out to be voltage related (battery, battery cables, alternator, drive belt).


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