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Old 10-12-2016, 10:16 PM   #1
Gaeilge1
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Default Not a transmission problem!


Hello: I'm new to this site and have what appears to be a somewhat unique problem with my 2001 Saturn LS with the 3.0 litre 6 cylinder engine. The problem is that once the vehicle reaches the speed or rpm's where it would naturally upshift, (going from say 1st to 2nd) the vehicle dies. Once I coax it along I can get it to shift to 2nd, but then when it should shift to 3rd it dies, then once I get it to 3rd and should be going to 4th it dies!! Once I do get to 4th or 5th I will be cruising down the highway at say 70 mph and all of a sudden without warning and without my pushing the accelerator I will be going 110 mph!!
I've had it in to two mechanics and discussed with a transmission specialist and all they have been able to tell me is that it is not the transmission. There are several diagnostic codes that have come up on a diagnostic scan but none of them either separately or in combination seem to explain what is going on. The pertinent codes appear to be: 502, 503, 506, 562, 563, 602, 603, 727, 741 and 757. There are some others but they don't appear related to this problem. I live in a rural area and the mechanics I've consulted are not very adept at electronic issues. I recognize that there are some issues with both speed sensors and the idle control.

My question is how difficult would it be to replace some of these sensors and relays and whether or not I can do it myself or need to take it to a specialist, (assuming I can find one in the area)? I'd appreciate any information I can get. Thanks, P.

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Old 10-16-2016, 06:13 AM   #2
derfderf
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p0502 Vehicle Speed Sensor Low input

The signal sent by the vehicle speed sensor to ECM is too low.
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p0503 Vehicle Speed Sensor 'A' Intermittent/Erratic/High

The signal sent by the vehicle speed sensor to ECM is too high or intermittent.

Since p0502 says low and p0503 says high/intermittent/ erratic, I'll go with erratic with a touch of intermittency for now

NOTE:
1) This means the car's PCM does not know how fast the vehicle is moving, which will affect ALL KINDS OF THINGS.
2) These 2 codes alone can result in shifting issues.
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p0506 - Idle Control System RPM Lower Than Expected

The idle speed is less than the target idle speed by 100 rpm or more.

Possible causes:

Dirty throttle body
Electric throttle control actuator misadjusted or damaged
Faulty Electric throttle control actuator
Intake air leak
Poor electrical connection to the Intake Air Control (IAC) valve

I'll GUESS at the electric throttle control actuator first because of your statement that the car uncontrollably speeds up on its own. Normally I would say throttle body clean b c IAC has junk stuck in it and vac leak check w carb or choke cleaner sprayed where the intake manifold runners meet the head. If you have a leaking intake gasket the rpm will change when the spray finds the leak and gets sucked in. DO BOTH before going after the throttle control actuator
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p0562 - Charging System Voltage Low

The Engine Control Module (ECM) has detected that the electrical system voltage level is out of range LOW.

Possible causes:

Low battery charge
Battery defective
Loose or missing alternator drive belt
Faulty alternator
Open or short system voltage circuit

Hmmmm -- what do all these problems have in common?
They are electrical signals.........
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p0563 (Charging) System Voltage High

The Engine Control Module (ECM) has detected that the electrical system voltage level is out of range HIGH.

Possible causes:

Battery defective
Loose or missing alternator drive belt
Faulty alternator
Open or short system voltage circuit

NOTE:
Higher than expected voltage problems are most likely caused by a bad voltage regulator. The voltage regulator is part of the alternator.
--------------------------------------------------------------------
Jackpot.

The car's ECM is, at times, not supplied enough operating current at the correct voltage and, at other times, supplied current at too high of a Voltage. Each situation can lead to a malfunctioning ECM, particularly the low V situation.

The voltage regulator is integrated into the alternator so you must replace the alternator.
Get a name brand one if you can (remanufactured is fine).

-----------------------------------------
BEFORE YOU SPEND A DIME:

1)Start the car in the driveway.
Measure the dc V across the battery terminals.
Should be about 14.4V will probably be all over the place. This is confirmation that the voltage regulator is defective.

2)Clear the codes and drive around a while, let the SES light turn on. Pull over somewhere and shut the car off for a minute -- take the key out when you turn it off. Purpose: Make the car think it is a 2nd trip since some codes do not trigger on a single trip, some take two or more trips to confirm the abnormal behavior is real and not just a glitch.Then restart and drive home. Counts
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If you are still throwing P0562 and P0563 it is the voltage regulator in the alternator because NO ECM will ever request the system voltage to be out of range.
****** I suppose there is a tiny chance it is not getting enough juice at the right operating conditions and is basically an underpowered computer issuing random nonsense commands but i HIGHLY doubt that since it can start and run the car (crappily, but run)*****
---------------------------------------
Conclusion:
Replace alternator
Clear codes
Report back on driveability and leftover codes


The IAC related codes should be ignored for right now
-------------------------------------------------------------------
(The only other code that made sense was the P0727 which was Engine Speed circuit no signal, because the voltage to the ECM was not correct so the signal circuit was not functioning properly)
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Old 10-17-2016, 04:31 PM   #3
Gaeilge1
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Thank you very much. I'm a little surprised that some of the geniuses around here couldn't figure this out!

I am very glad I joined this site and at least now have decent explanation of what might be wrong that makes sense!
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Old 10-23-2016, 07:31 AM   #4
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Hellooooooooooooooooooooooooooo................... ?
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Old 10-31-2016, 03:24 PM   #5
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Would be really cool if you'd come back and let us know the fix or lack thereof.
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