2002 Saturn Vue AWD V6 power loss, SES

[TerdRatchett]

Hi Friends!

I have a 2002 Saturn Vue AWD V6 and am experiencing severe power loss and the SES light is staying on.

I depress the accelerator in park and watch the engine RPMs go up slowly. I can hold it at any RPM but it takes several seconds to get there and I can hear the TP flapper slap each time I vary the accel position.

When I drive the vehicle it takes a long time to get up to speed. If I let it accelerate slowly the vehicle shifts normally thru the gears. Max speed seems to be about 45 on the flat. If I depress the accelerator hard from stop the engine RPMs come up sluggishly and the transmissions shifts hard as it goes thru the gears.

There is a stong odor of partially unspent fuel coming from the exhaust. In addition there is a pinging noise apparently coming from the catalytic converters or the exhaust pipes underneath the car in a short time after the vehicle is started and when turned off and cooling down.

After experiencing these problems for some time I borrowed a friends test system and checked the error codes:

P1779
P1780
P0997
P0705
P0700
P2119
P0300
P0306
P0302
P0221

I then cleared the codes and ran the car around the block. The SES engine was off at first but then came back on. Checking the codes again I found just four errors:

P1779
P1780
P0700
P0221

Here is my troubleshooting logic, please advise.

The smell of the exhaust gives an indication that it is running far too rich. The cats do not appear to be plugged as I seem to be getting good pressure at the exhaust. The excessive heating of the exhaust pipes also indicate unspent fuel burning off. I have checked the kick panel connectors that lead to the ecu and the connections look pristine.

I believe the P1779 and P1780 codes are secondary errors and not directly related to the actual problem. I am guessing that the TCU is requesting a torque reduction from the ECU for a smooth shift but that the primary error is not allowing the torque reduction to occur. The P0700 might also be a secondary error as I attempted to rev the car and it shifted hard several times. The P0221 error I believe is the primary error and the indicator of the
trouble.

There is a bulletin that has to do with P0221 and the SES light coming on that targets the throttle body, throttle body connector and terminals wires. The fact I can hold any desired RPM in park seems to indicate that the accelerator potentiometer is working correctly. I think the ECU itself is working correctly. I suspect the ECU is getting bad information from the
throttle position potentiometer so it is trying to keep the car running by using just the O2, MAF and crank position sensor data to operate in limited power mode. The clunking of the throttle flap would indicate that the servo itself is functioning but the ECU is hunting for the throttle position and not finding it. The ECU doesn't know the throttle flap position for sure and is running very rich because it is using best guesses.

So basically I am blaming the throttle body. Any thoughts?

Thanks in advance,
TR

[far2grumpy]

Sounds logical ... have you unplugged the TB control module to check for corrosion on either the TB or cable connectors?

It isn't clear to me that you have the description for SES code P0221 so here's a paste from service manual:

The throttle position (TP) sensors 1 and 2 are located within the throttle body assembly. The TP sensors share a common 5-volt reference circuit and a common low reference circuit. The 5-volt reference circuit is also shared with the accelerator pedal position (APP) sensor 2. The 5-volt reference voltage is supplied on two separate engine control module (ECM) terminals, but the terminals are connected internally to the same voltage supply. Each TP sensor has an individual signal circuit, which provides the ECM with a signal voltage proportional to throttle the plate movement. When the throttle plate is in the closed position, the TP sensor 1 signal voltage is near the low reference and increases as the throttle plate is opened. The TP sensor 2 signal voltage at closed throttle is near the 5-volt reference and decreases as the throttle plate is opened. The ECM compares the signal of the TP sensors to the mass air flow (MAF) sensor when the engine is running to determine if the sensor readings are correct. The control module also compares the signal of the TP sensor 1 and TP sensor 2 through the entire range. If the ECM detects a difference of more than 6 percent between sensor 1 and sensor 2, and a difference from the predicted range by more than 9 percent, DTC P0221 sets.

[Chazberry]

Just for laughs, check your Alternator voltage. The only time I had a loss of power with my L81 was when the Alternator went south.

[TerdRatchett]

Hi Far2grumpy,

Thanks very much for your post. I appreciate the info from the service manual, there is a lot of useful information that will help.

I did initially unplug and carefully inspect the TB control module. Based on the bulletin I mentioned I almost expected the wiring at the connector to be a mess. Just the opposite, the connector, wire, crimp and terminals look pristine. Everything externally looks almost new.

I decided to shell the TB and look inside. Protected by a rubber gasket the inside of the unit also looked in very good shape. One potential problem I saw was some wear on the carbon tracks for the position potentiometers, although not nearly enough to cause problems in my opinion. The other problem seems to be more likely, reduced spring pressure on the pot wipers. I bent the spring contacts ever so slightly to apply a bit more pressure and when I put it back together I could feel the swipes touch about .010" before the halves mated.

For reference I found the top and longest of the 4 carbon tracks to measure about 1055 ohms from end to end. The next one down is technically the wiper arm and is 303 ohms from end to end. The third is about 1055 ohms from end to end, but since I discovered the first and third are in parallel I suspect they are about 2K ohms each. The short wiper for the second pair is only 11.5 ohms from end to end.

After re-assembly I measured the resistances at the connector.

Connector pins 3 and 6 are the top sensor:
Fully open = 552 ohms
Fully closed = 1463 ohms

Connector pins 2 and 5 are the bottom sensor:
Fully open = 476 ohms
Fully closed = 1333 ohms

Both sensors seem to track well across the full range of the throttle position. I'm no math expert but in terms of percent of difference in resistance that seems more than 9% between sensors.

I reinstalled the TB on the car and went thru the reset procedure. No noticeable difference, the vehicle still has little power and sluggish response. The SES light was out for the first minute but came back on after test run.

Considering next plan of action. Ideas and thoughts are welcome and appreciated.

TIA,
TR

[TerdRatchett]

Hi Chazberry,

Thanks for the idea, if we ever get a break from this rain I will check the alternator charge voltage. I have not had a reason to suspect it since the car has not given me any sluggish starts, but you can't assume anything with modern technology!

Talk soon,
TR

[far2grumpy]

Originally Posted by TerdRatchett

Hi Far2grumpy,

Thanks very much for your post. I appreciate the info from the service manual, there is a lot of useful information that will help.

I did initially unplug and carefully inspect the TB control module. Based on the bulletin I mentioned I almost expected the wiring at the connector to be a mess. Just the opposite, the connector, wire, crimp and terminals look pristine. Everything externally looks almost new.

I decided to shell the TB and look inside. Protected by a rubber gasket the inside of the unit also looked in very good shape. One potential problem I saw was some wear on the carbon tracks for the position potentiometers, although not nearly enough to cause problems in my opinion. The other problem seems to be more likely, reduced spring pressure on the pot wipers. I bent the spring contacts ever so slightly to apply a bit more pressure and when I put it back together I could feel the swipes touch about .010" before the halves mated.

For reference I found the top and longest of the 4 carbon tracks to measure about 1055 ohms from end to end. The next one down is technically the wiper arm and is 303 ohms from end to end. The third is about 1055 ohms from end to end, but since I discovered the first and third are in parallel I suspect they are about 2K ohms each. The short wiper for the second pair is only 11.5 ohms from end to end.

After re-assembly I measured the resistances at the connector.

Connector pins 3 and 6 are the top sensor:
Fully open = 552 ohms
Fully closed = 1463 ohms

Connector pins 2 and 5 are the bottom sensor:
Fully open = 476 ohms
Fully closed = 1333 ohms

Both sensors seem to track well across the full range of the throttle position. I'm no math expert but in terms of percent of difference in resistance that seems more than 9% between sensors.

I reinstalled the TB on the car and went thru the reset procedure. No noticeable difference, the vehicle still has little power and sluggish response. The SES light was out for the first minute but came back on after test run.

Considering next plan of action. Ideas and thoughts are welcome and appreciated.

TIA,
TR

The throttle body (TB) resistance values are great - I've never even suspected a ball-park figure for those resistors.

I've attached a thumbnail schematic in case you don't have the interconnect.

The ECM compares the voltages available on pins 5 and 6 - which will obviously be different at any particular point - depending on throttle blade angle.

If the TB resistors are basically linear through the range - voltages differences felt at ECM outside the "predicted range" could be due to wiring resistance between TB and ECM - or perhaps something in ECM has gone haywire. (Fingers are crossed that Chazberry nailed it with the low-voltage suggestion).

I suspect since the SB made a big deal about installing a new TB connector it would make sense to check wire continuity/resistance between the TB connector and ECM connector.

Just a suggestion.