Vehicle had been running. Had a cold snap with single digit temperatures...vehicle hadn't been started for 4 or 5 days. .tried to start it, wouldn't start. Had it towed to a Chev dealership, they put a code reader on it, showed P0621, they said we needed a new battery and alternator. Bought both and had them installed. Still won't start. Had old alternator tested, it is still good.
Without testing we'd only be guessing ! You have no idea of the complexity of the electronics on your vehicle . Replacing the ECM would mean a trip back to the dealer to have it programmed . Without programming your vehicle will never start . You had new battery an alternator installed , did it start an run when you picked it up. The charging system on your vehicle is computer controlled . DTC P0621
DTC P0621 : Generator L-Terminal Circuit
The engine control module (ECM) uses the generator turn ON signal circuit to control the load of the generator on the engine. A high side driver in the ECM applies a voltage to the voltage regulator. This signals the voltage regulator to turn the field circuit ON and OFF. The ECM monitors the state of the generator turn ON signal circuit. The ECM should detect low voltage on generator turn on signal circuit when the ignition is ON and the engine is OFF, or when the charging system malfunctions. With the engine running, the ECM should detect high voltage on the generator turn on signal circuit. The ECM performs key ON and RUN tests to determine the status of the generator turn on signal circuit.
Your best bet take it back to the dealer .
For ignition switch power modes refer to Body Control System Description and Operation . When the ignition switch is placed in the Start position a discrete signal is supplied to the body control module (BCM) notifying it that the ignition is in the Start position. The BCM then sends a message to the engine control module (ECM) notifying it that CRANK has been requested. At the same time the BCM is supplying 12 volts for the IGN 1 relay closing it and supplying battery positive voltage for the crank relay coil. The ECM verifies that the transmission is in Park or Neutral. If it is, the ECM grounds the control circuit of the crank relay. When this occurs battery positive voltage is supplied through the switch side of the crank relay to the S terminal of the starter solenoid.
It starts and runs but battery not charging...code still comes up P0621...charging system failure shows on message display.
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SOURCE: Looking for location of ECM
Hope this helps
UPLANDER 06 Elec Cont Unit (ECU); (left front of engine compartment), 3.5L.
http://cgi.ebay.com/ebaymotors/2006-Chevy-Uplander-Engine-Computer-PCM-ECM-12600928_W0QQcmdZViewItemQQ_trkparmsZ72Q3a1205Q7c66Q3a2Q7c65Q3a12Q7c39Q3a1Q7c240Q3a1318QQ_trksidZp3286Q2ec0Q2em14QQhashZitem320315289651QQitemZ320315289651QQptZMotorsQ5fCarQ5fTruckQ5fPartsQ5fAccessories
SOURCE: Needing to locate the airbag control module '07 caliber
it is located behind the floor shifter in center console..under small piece of carpet
SOURCE: reduce engine power 2007 chevy uplander
Sopunds like the computer has gone into a limp mode. You need to take it in for a professional diagnosis.
SOURCE: fuel filter for the chevy uplander
The fuel filter on this vehicle is located inside the fuel tank and is an integral part of the fuel pump module assembly. As such, it's not replaceable by itself and can only be serviced by replacing the entire pump module. It's a "lifetime" filter, in theory anyway, but it can plug up if there has been a large amount of crud that has gotten into the tank somehow. The best way to determine if the filter is restricted is to have the fuel pressure tested as part of a road test drive to see if the pressure remains steady [indicating a good pump and ok filter] or drops off [indicating a restricted filter or weak pump] Hope this helps!
SOURCE: my 2008 chevy uplander engine
You will need to get the codes checked.This will help in finding out what is causing the light to come on.Once you get the code or codes we can find out what could be causing the problem.Let me know when you get the codes and I`ll be glad to help you out.Good luck.
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