[This post replaces a previous post with corrections and additional info]

I have an 08 LR2 and checked the Live Data sensor readings using an XTool OBD2 scanner (screenshots attached). As previously stated by others, a healthy battery and alternator are a minimum requirement before any of these readings can be relied upon.

For the pedal position sensor, not depressed, circuit D is 7.06 and circuit E fluctuates between 7.84 - 8.24.

Code P2138 may also indicate a problem with the throttle position sensor on the throttle body. With the pedal not depressed at idle, sensor-1 is 0.71 and sensor-2 is 1.56. So sensor-1 correlates at approx half of sensor-2.

Your pedal sensor readings match mine closely. What are your throttle sensor readings?

 

Not questioning anyone's knowledge or experience here, just wondering if I'm taking the correct steps. Would a low battery explain P0642 - Sensor Reference Voltage A Circuit Low and P0069 - Manifold Absolute Pressure Barometric Pressure Correlation along with the P2138, and "Engine Performance Reduced? The car will crank and start for a few seconds and die. Because of that I can't even check the alternator.

I've only owned the car for 2 years so I don't know how long the battery has been in service. It does have a sticker that says Jun 22 so I assume that is the manufacturing date.

When all of this started a month ago charging the battery was the first thing I did and it has held a charge pretty well. I figured if it is a little below 12 volts now it is due to trying to start it while testing and troubleshooting. I don't think I said this earlier, when I key on, push the start button without pressing the brake pedal, the dash says it is doing a system check and it will give a message of Engine Performance Reduced. It seems the controller won't let it start as long as that is active. A lot of you have said that the battery being a little low can cause issues so I'll accept the advice and try replacing the battery.

LR2 Driver, thanks for checking yours readings. It sounds like the APP_E signal fluctuating isn't abnormal. Below are photos of the scanner readings you mentioned plus a few others. I'm not sure if the TP_R and TP_B not being the same is an issue. This is just key on since the engine won't start. If you all say a weak battery can cause the sensor readings to be unreliable I won't chase any of these until a new battery is installed.



MAP, Barometric pressure, Throttle Position readings, APP readings

APP_E signal graphed

Battery reading and scanner reading for controller voltage with key on

 

Your TP_R and TP_ B readings are the angle positions of the throttle body. They are different measurements than the throttle position sensor readings I provided which are related to code P2138.

 

Yes a bad battery (or alternator) will cause all sorts of electrical gremlins on this car.

On the cars we grew up with, a bad battery would just mean harder starts until eventually it wouldn't start. This car is different.

Jun 22 means the battery was installed then. That's old enough to have issues if it was maybe drained a few times. Or if it's a wet cell that hasn't had the acid level topped up (with distilled water). Or any battery can be defective at any time. I'd get it tested before going down the other rabbit holes.

EDIT: I can see in the pic that it is a wet cell battery. Pull it out, top off the acid level, then get it charged and tested. If the acid is very low it might be ruined anyway, those should really be checked annually. Yes it's a PITA which is why sealed or AGM batteries are nice (though more costly). Since the mfgs sticker is covering the cell access plug that it's in the pic, I'm guessing the battery hasn't been maintained.

If cost is an issue, FLAPS will charge and test it for free.

 

I’m not familiar with FLAPS. Is that an auto parts store? I have AutoZone, O’Riley’s, and Napa near me and I think most of them test for free.

Yeah, in my 49 years dealing with cars this is the first one I’ve dealt with that wouldn’t start even if the battery has enough juice to turn it over.

 

Friendly Local Auto Parts Store, any of the ones you mentioned.

First one for me too.

 

Old battery was tested and the cranking amps were about 700, so a little weak but volts were above 12 so the kid at the FLAPS said it was fine. I went ahead and purchased and installed a new AGM battery anyway. Still have Engine Performance Reduced message on dash with key on. The first time I try to start it after connecting the battery it will fire a few times but sputter and die after maybe 5 seconds. I checked that the alternator is spinning when the starter is cranking.

I used the scan tool and it still had some active codes in the memory so I cleared the codes. .The live data still shows the MAP at 1.9 psi while the barometric reading is 12.5 psi. I know this was an issue a few months ago that was corrected with a new MAP sensor so I have a replacement on order from the FLAPS. The voltage reading from the ECM was at 12.2 volts with the new battery instead of 11.8 volts so that is an improvement.

When I removed the old battery there was hose underneath it (see image below) that doesn't look like it should be where it was. I'm not sure where it is supposed to connect. Any suggestions?


Mystery hose in battery box