Malfunction light on. rapping sound in engine when stepping on or letting off gas.

Not much you can do unless you want to buy a $5,000 Professional Grade Scan tool computer.

https://www.google.com/search?q=2004+Chevy+Impala.+How+can+I+troubleshoot+the+Retained+Accessory+Power

https://www.google.com/search?q=auto+electrician+near+me

..

do the power windows keep working too. . , Retained Accessory Power (RAP) .

Retained accessory power (RAP) is a standard feature. RAP allows the radio, power windows, and if equipped, power sunroof and cellular telephone to operate for approximately 10 minutes after the ignition switch has been turned to OFF, or until a passenger compartment door is opened.

The dash integration module (DIM) monitors and determines the ignition switch status (OFF, ACCESSORY, etc.). When the DIM determines that the ignition switch has been turned to the OFF position, the DIM sends a class 2 serial data message to the radio, drivers door module (DDM), rear integration module (RIM) and cellular telephone module (if equipped) in order to enable the RAP. After approximately 10 minutes the DIM sends another class 2 serial data message in order to disable the RAP.
The DIM receives door status (OPEN, CLOSED) from the DDM by a class 2 serial data line message. When the DIM determines that a passenger compartment door has been opened, the DIM sends out a class 2 serial data message in order to disable the RAP, regardless of the elapsed time.


2000 Buick LeSabre ' LeSabre (VIN H) Service Manual ' Body and Accessories ' Retained Accessory Power ' Diagnostic Information and Procedures ' Document ID: 475077
--------------------------------------------------------------------------------
Retained Accessory Power (RAP) On After Timeout

Step
Action
Value(s)
Yes
No
1
Did you perform the Retained Accessory Power (RAP) Diagnostic System Check?
--
YES - Go to Step 2
NO - Go to Diagnostic System Check - Retained Accessory Power
2
Install a scan tool.
Close all of the doors.
Turn ON the ignition, with the engine OFF.
Wait 5 seconds, then turn OFF the ignition.
Wait 10 minutes.
Observe the dash integration module (DIM) ignition switch status.
Does the ignition switch status indicate OFF?
--
YES - Go to Step 3
NO - Go to DTC B1422 Device Power Moding Malfunction

Observe the RAP Output parameter in the rear integration module (RIM) data list.
Does the RAP Output indicate OFF?
--
YES - Go to Step 4
NO - Go to Step 10
4
Turn ON the ignition, with the engine OFF.
Using the scan tool, command the RAP relay ON and OFF.
Does the RAP relay turn ON and OFF with each command?
--
YES - Go to Step 8
NO - Go to Step 5
5
Connect a test lamp between the control circuit of the RAP relay and the coil side feed circuit of the RAP relay.
Using the scan tool, command the RAP relay ON and OFF.
Does the test lamp turn ON and OFF with each command?
--
YES - Go to Step 8
NO - Go to Step 6

6
Does the test lamp remain illuminated with each command?
--
YES - Go to Step 7
NO - Go to Step 10
7
Test the control circuit of the RAP relay for a short to ground. Refer to Circuit Testing and Wiring Repairs in Wiring Systems.
Did you find and correct the condition?
--
YES - Go to Step 13
NO - Go to Step 10
8
Test the load output circuit of the RAP relay for a short to voltage. Refer to Circuit Testing and Wiring Repairs in Wiring Systems.
Did you find and correct the condition?
--
YES - Go to Step 13
NO - Go to Step 9
9
Inspect for poor connections/terminal tension at the RAP relay. Refer to Testing for Intermittent Conditions and Poor Connections and Connector Repairs in Wiring Systems.
Did you find and correct the condition?
--
YES - Go to Step 13
NO - Go to Step 11
10
Inspect for poor connections/terminal tension at the harness connector of the RIM. Refer to Testing for Intermittent Conditions and Poor Connections and Connector Repairs in Wiring Systems.
Did you find and correct the condition?
--
Go to Step 13
Go to Step 12
11
Replace the RAP relay.
Did you complete the replacement?
--
Go to Step 13
--
12
Replace the RIM. Refer to Rear Integration Body Control Module Replacement in Body Control System.
Did you complete the replacement?
--
Go to Step 13
--
13
Operate the system in order to verify the repair.
Did you correct the condition?
--
System OK
Go to Step 1





Without testing using the above factory diagnostic test proceduces , i would probably guess the rap relay has stuck contacts inside .

Did you check for BCM codes
DTC B1477
Retained Accessory Power Circuit Low
DTC B1478
Retained Accessory Power Circuit High
DTC B1397
Device Voltage Reference Out #1 CKT Low
DTC B1398
Device Voltage Reference Out #1 CKT High
Charging system check ?

Diagnostic System Check - Retained Accessory Power
Test Description
The numbers below refer to the step numbers on the diagnostic table.

1. Lack of communication may be due to a partial malfunction of the class 2 serial data circuit or due to a total malfunction of the class 2 serial data circuit. The specified procedure will determine the particular condition.


2. This step is checking for DTCs in the BCM.


3. This step is checking for RAP specific DTCs.

Step

Action

Yes

No

1

Install a scan tool.

Does the scan tool power up?
Go to Step 2
Go to Scan Tool Does Not Power Up in Data Link Communications

2

1. Turn ON the ignition, with the engine OFF.
2. Attempt to establish communication with the body control module.

Does the scan tool communicate with the BCM?
Go to Step 3
Go to Scan Tool Does Not Communicate with Class 2 Device in Data Link Communications

3

Important: The engine may start during the following step. Turn OFF the engine as soon as you have observed the Crank power mode.

1. Access the Class 2 Power Mode in the Diagnostic Circuit Check on the scan tool.
2. Rotate the ignition switch through all positions while observing the Class 2 Power Mode on the Scan Tool. Refer to the Serial Data Power Mode table within the Body Control System Description and Operation in Body Control Systems, for a list of the power mode states that correspond to each ignition switch position.

Does the Class 2 Power Mode parameter reading match the ignition switch position for all the selected positions?
Go to Step 4
Go to Power Mode Mismatch in Body Control System

4

Select the BCM display DTCs function on the scan tool.

Does the scan tool display any DTCs?
Go to Step 5
Go to the Symptoms list in the appropriate service category

5

Does the scan tool display B1477 or B1478?
Go to Diagnostic Trouble Code (DTC) List
Go to Symptoms - Retained Accessory Power

let auto zone code scan for free see what causing check engine light to flash on.could have faulty tps sensor faulty egr valve or idle speed contol valve.

Oil might be low or the oil pump might be malfunctioning

Is your check engine light on?

It sounds like it could be you TPS (throttle position sensor)

If it's not getting the right signal when you step on the gas pedal, it won't let the computer know what position it's in, when the throttle is open it will let in to much air, but not give it enough fuel for that amout of air.....

that code is for a MIL indicator malfunction-in other words, your check engine light is malfunctioning...do you have a MIL light that works when you turn you key on, before starting? If not, the bulb is blown out, and you should replace it. If it does work, I'd suggest disconnecting the negative battery cable and letting the car sit for 5 minutes, then start it up and let it idle (no gas at all) for 5 minutes, then drive it lightly for another 5-if the light stays on, you have a malfunction with either the wiring to the light or possibly the ECM.

Sounds like a cam positioning sensor. The vehicle needs to be connected to a diagnostic scan tool to look at parameters. Unless you are hearing a noticeable rapping noise from rockers I wouldn't worry about it. If you find a malfunction on that circuit, check the wiring and the condition of the plug before condemning the sensor.

Turn key ignition forward but do not start engine. Pump gas pedal fully 3 times then engine light will start flashing. Do not pump gas pedal short quick pumps. After light is flashing turn ignition off then start engine. The check engine will reset it's self.

Exhaust Gas Recirculation (EGR) System The exhaust gas recirculation (EGR) system recirculates exhaust gas into the intake manifold (9424). This lowers combustion temperatures and reduces the formation of oxides of nitrogen (NOX). The amount of exhaust gas reintroduced and the timing of the cycle varies by calibration. Timing and volume are controlled by the powertrain control module (PCM) (12A650). The EGR valve (EGR valve) (9D475) is vacuum actuated. The vacuum hose routing diagram is shown on the Vehicle Emission Control Information (VECI) decal. EGR operation stops when the engine temperature is cold, to improve driveability. The PCM controls the EGR solenoid vacuum valve (9D474). When energized the intake manifold vacuum outlet fitting and cap (9A474) allows exhaust gas to be circulated in the engine to be burned.