Dreams190

I bought my car (03 z06 w/ 42,000 miles) about 6 months ago and been having this issue off and on...

after a spirited drive through the gears, coming up to red lights the engine has a tendency to dip to about 500rpm and sometimes even stall completely. It also seems like it isn't quite making the power/torque it should be and it smokes gray a little under high load. It still pulls alright but not quite the way a 390whp car should. Tires won't even break loose in 1st or even with a hard shift into 2nd. They used to spin through 1st, and all the way to the top of 2nd.

I've only had the car set a hard code and give me the "reduced engine power" warning 1 time. P0101 and some random TCS codes (1247 is the one that keeps popping up)

Mods by the previous owner are Vararam, LG street longtubes, x-pipe, and a custome tune.... since I've owned the car I've done a Corsa catback, Yellaterra 1.8 rockers, and MSD wires


I know the P0101 is a MAF code, should I be replacing that first? That was my first shot from the hip, and then I was gonna go back to a stock tune. I'd hate to lose my tune and hp/tq only to find that it isn't the problem though...


Sorry for the long read guys!
Rob

tmqdoc1

If you havent already done so I would make sure everything forward of the throttle body is connected tightly and in place as well as cleaning the maf sensor. If you find anything wrong fix it and then disconnect the battery for a few minutes and then reconnect. gl

Dreams190

I'll check all the seals again tomorrow, but I've tried cleaning the MAF, as well as disconnecting the battery... Several times, lol

DefenderC5

Just a few more things to try as you troubleshoot:

Here's a link for your 1247 code

http://forums.corvetteforum.com/show...33&postcount=3

Has this problem been off and on since you got the vehicle? Who did your "custom tune"? When was the last time you cleaned your filters? Did you overoil them and gum up the MAF?

Also, don't forget to clean your grounds (it has caused your codes before)
http://forums.corvetteforum.com/showthread.php?t=896875

Bill Dearborn

That reference to my previous post on DTC 1247 doesn't fit your car. The previous post involved a 2000 C5 while yours is a 2003. With the change in the ABS system that occurred in the 2001 model year DTC 1247 became this:

DTC C1247
Circuit Description
The brake fluid level switch monitors the level of brake fluid in the master cylinder. When the IPC sees the brake fluid level switch input grounded, it turns ON the red Brake indicator and sends a serial data message to the EBCM that tells the EBCM that the brake fluid level is low.

Conditions for Running the DTC
The ignition is ON.

Conditions for Setting the DTC
The EBCM receives a serial data message from the IPC indicating that the brake fluid level is low.

Action Taken When the DTC Sets
The EBCM disables the TCS/VSES until the DTC becomes a history DTC.
The red Brake warning indicator turns ON.
The Traction Control and Active Handling indicator turns ON.
The DIC displays the following messages:
Low Brake Fluid
Service Traction System
Service Active Handling
The ABS remains functional.
Conditions for Clearing the DTC
The condition for the DTC is no longer present and the DTC is cleared with a scan tool.
The EBCM automatically clears the history DTC when a current DTC is not detected in 100 consecutive drive cycles.
Diagnostic Aids
Inspect the master cylinder reservoir for the proper brake fluid level.

Step
Action
Yes
No

Schematic Reference: Brake Warning System Schematics

Connector End View Reference: Hydraulic Brakes Connector End Views or Instrument Panel, Gages, and Console Connector End Views

Step 1
Did you perform the Hydraulic Brake Diagnostic System Check?
Go to Step 2
Go to Diagnostic System Check - Hydraulic Brakes

Step 2
Inspect the brake fluid level.

Is the brake fluid level OK?
Go to Step 3
Go to Brake Fluid Loss

Step 3
Install a scan tool.
Turn ON the ignition, with the engine OFF.
With a scan tool, observe the Brake Fluid Level parameter in the Instrument Panel Cluster data list.
Does the scan tool indicate that the Brake Fluid Level parameter is OK?
Go to Testing for Intermittent and Poor Connections in Wiring Systems
Go to Step 4

Step 4
Turn OFF the ignition.
Disconnect the brake fluid level switch.
Turn ON the ignition, with the engine OFF.
With a scan tool, observe the Brake Fluid Level parameter.
Does the scan tool indicate that the Brake Fluid Level parameter is OK?
Go to Step 6
Go to Step 5

Step 5
Test the signal circuit of the brake fluid level switch for a short to ground. Refer to Circuit Testing and Wiring Repairs in Wiring Systems.

Did you find and correct the condition?
Go to Step 10
Go to Step 7

Step 6
Inspect for poor connections at the harness connector of the brake fluid level switch. Refer to Testing for Intermittent and Poor Connections and Connector Repairs in Wiring Systems.

Did you find and correct the condition?
Go to Step 10
Go to Step 8

Step 7
Inspect for poor connections at the harness connector of the instrument cluster (IPC). Refer to Testing for Intermittent and Poor Connections and Connector Repairs in Wiring Systems.

Did you find and correct the condition?
Go to Step 10
Go to Step 9

Step 8
Replace the brake fluid level switch. Refer to Master Cylinder Fluid Level Sensor Replacement .

Did you complete the repair?
Go to Step 10
--

Step 9
Replace the instrument cluster (IPC). Refer to Instrument Panel Cluster (IPC) Replacement in Instrument Panel, Gauges and Console.

Did you complete the repair?
Go to Step 10
--

Step 10
Operate the system in order to verify the repair.

Did you correct the condition?
System OK
Go to Step 2

Here is the diagnostic for your P0101:

DTC P0101

Circuit Description
The mass air flow (MAF) sensor is an air flow meter that measures the amount of air entering the engine. The powertrain control module (PCM) uses the MAF sensor signal to provide the correct fuel delivery for all engine speeds and loads. A small quantity of air entering the engine indicates a deceleration or idle condition. A large quantity of air entering the engine indicates an acceleration or high load condition. The MAF sensor has the following circuits:
• An ignition 1 voltage circuit
• A ground circuit
• A signal circuit
The PCM applies a voltage to the sensor on the signal circuit. The sensor uses the voltage to produce a frequency based on the inlet air flow through the sensor bore. The frequency varies within a range of near 2,000 Hertz at idle to near 11,500 Hertz at maximum engine load. The PCM uses the following sensor inputs to calculate a predicted MAF value:
• The manifold absolute pressure (MAP) sensor
• The intake air temperature (IAT) sensor
• The engine coolant temperature (ECT) sensor
• The engine speed (RPM)
The PCM compares the actual MAF sensor frequency signal to the predicted MAF value. This comparison will determine if the signal is stuck based on a lack of variation, or is too low or too high for a given operating condition. If the PCM detects the actual MAF sensor frequency signal is not within a predetermined range of the calculated MAF value DTC P0101 sets.

Conditions for Running the DTC
• DTCs P0102, P0103, P0106, P0107, P0108, P0440, P0442, P0446, P0449, P1120, P1220, P1221, P1441 are not set.
• The engine is running.
• The ignition 1 signal is between 11 and 18 volts.
• The throttle position (TP) indicated angle is less than 95 percent.
• The change in the TP indicated angle is less than 5 percent.
• The MAP sensor is more than 17 kPa.
• The change in the MAP sensor is less than 3 kPa.
• The above conditions are met for 1.5 seconds.

Conditions for Setting the DTC
The PCM detects that the actual MAF sensor frequency signal is not within a predetermined range of the calculated MAF value for more than 4 seconds.

Action Taken When the DTC Sets
• The control module illuminates the malfunction indicator lamp (MIL) on the second consecutive ignition cycle that the diagnostic runs and fails.
• The control module records the operating conditions at the time the diagnostic fails. The first time the diagnostic fails, the control module stores this information in the Failure Records. If the diagnostic reports a failure on the second consecutive ignition cycle, the control module records the operating conditions at the time of the failure. The control module writes the operating conditions to the Freeze Frame and updates the Failure Records.

Conditions for Clearing the MIL/DTC
• The control module turns OFF the malfunction indicator lamp (MIL) after 3 consecutive ignition cycles that the diagnostic runs and does not fail.
• A current DTC, Last Test Failed, clears when the diagnostic runs and passes.
• A history DTC clears after 40 consecutive warm-up cycles, if no failures are reported by this or any other emission related diagnostic.
• Clear the MIL and the DTC with a scan tool.

Diagnostic Aids
• Inspect the harness of the MAF sensor to verify that it is not routed too close to the following components:
o The secondary ignition wires or coils
o Any solenoids
o Any relays
o Any motors
• A low minimum air rate through the sensor bore at idle or during deceleration may cause this DTC to set. Inspect for the following conditions:
o Any deposits on the throttle plate or in the throttle bore
o Any vacuum leak downstream of the MAF sensor
• Inspect for any contamination or debris on the sensing elements of the MAF sensor.
• Inspect the air induction system for any water intrusion. Any water that reaches the MAF sensor will skew the sensor and may cause this DTC to set.
• Inspect the secondary air injection system (AIR) for any water intrusion.
• A wide open throttle acceleration from a stop should cause the MAF sensor parameter on the scan tool to increase rapidly. This increase should be from 7-12 g/s at idle to 200 g/s or more at the time of the 1-2 shift. If the increase is not observed, inspect for a restriction in the induction system or the exhaust system.
• Inspect for a skewed or stuck ECT sensor.
• A high resistance of 15 ohms or more on the ignition 1 voltage circuit may cause the DTC to set. A high resistance may cause a driveability concern before this DTC sets.
• The barometric pressure that is used to calculate the predicted mass air flow value is initially based on the MAP sensor at key ON. When the engine is running the MAP sensor value is continually updated near wide open throttle. A skewed MAP sensor will cause the calculated mass air flow value to be inaccurate and may result in a no start condition. The value shown for the MAP sensor display varies with the altitude. With the ignition ON and the engine OFF, 103 kPa is the approximate value near sea level. This value will decrease by approximately 3 kPa for every 305 meters (1,000 feet) of altitude.
• A high resistance on the low reference circuit of the MAP sensor may cause this DTC to set.
If the condition is intermittent, refer to Intermittent Conditions .

Test Description
The numbers below refer to the step numbers on the diagnostic table.
5. This step will determine if the MAP sensor pressure is within the proper range for a given altitude.
6. This step will determine if the MAP sensor voltage is within the proper range at idle.
7. This step will determine if the MAP sensor responds properly to the change in manifold pressure.
8. This step will determine if the throttle position (TP) sensors are operating properly.
9.This step will determine if any mechanical faults have caused this DTC to set.
10. This voltage drop will determine if high resistance has caused this DTC to set.
Step Action Values Yes No
Schematic Reference: Engine Controls Schematics
Connector End View Reference: Powertrain Control Module (PCM) Connector End Views or Engine Controls Connector End Views

Step 1
Did you perform the Diagnostic System Check-Engine Controls? -- Go to Step 2
Go to Diagnostic System Check - Engine Controls

Step 2 Attempt to start the engine.
Does the engine start? -- Go to Step 3
Go to Step 5

Step 3 Observe the Diagnostic Trouble Code (DTC) Information with the scan tool.
Does the scan tool display any other DTCs set? -- Go to Diagnostic Trouble Code (DTC) List
Go to Step 4

Step 4
1. Observe the Freeze Frame/Failure Records for this DTC.
2. Turn OFF the ignition for 30 seconds.
3. Start the engine.
4. Operate the vehicle within the Conditions for Running the DTC. You may also operate the vehicle within the conditions that you observed from the Freeze Frame/Failure Records.
Did the DTC fail this ignition? -- Go to Step 5
Go to Diagnostic Aids

Step 5
Important:
The Altitude vs. Barometric Pressure table indicates a pressure range for a given altitude under normal weather conditions. Weather conditions consisting of very low or very high pressure and/or temperature may cause a reading to be slightly out of range.
1. Turn ON the ignition, with the engine OFF.
2. Observe the MAP sensor kPa parameter with a scan tool.
3. The MAP sensor pressure should be within the specified range for your altitude. Refer to Altitude vs Barometric Pressure .
Is the MAP sensor pressure within the specified range? -- Go to Step 6
Go to DTC P0106

Step 6
1. Start the engine.
2. Turn off all accessories.
3. Allow the engine to reach operating temperature.
4. Observe the MAP sensor parameter with a scan tool .
Is the MAP sensor parameter within the specified range? 0.8-3 V Go to Step 7
Go to DTC P0106

Step 7
1. Idle the engine.
2. Observe the MAP sensor parameter with a scan tool.
3. Increase the engine speed slowly to 3,000 RPM and then back to idle.
Does the MAP sensor parameter change smoothly and gradually through the specified range of the test? -- Go to Step 8
Go to DTC P0106

Step 8
1. Turn OFF the ignition for 30 seconds.
2. Turn ON the ignition with the engine OFF.
3. Observe the TP indicated angle parameter with a scan tool.
4. Depress the accelerator pedal completely.
Is the TP indicated angle parameter within the specified range? 95-100% Go to Step 9
Go to DTC P1120

Step 9
1. Turn OFF the ignition.
2. Inspect for the following conditions:
o A restricted or collapsed air intake duct
o A misaligned air intake duct
o A dirty or deteriorating air filter element
o Any objects blocking the air inlet screen of the MAF sensor
o Any contamination or debris on the sensing elements of the MAF sensor
o Any water intrusion in the induction system
o Any water intrusion in the AIR system
o Any vacuum leak downstream of the MAF sensor
o A skewed or stuck ECT sensor
o Any type of restriction in the exhaust system. Refer to Restricted Exhaust in Engine Exhaust.
Did you find and correct the condition? -- Go to Step 14
Go to Step 10

Step 10
1. Disconnect the harness connector of the MAF sensor.
2. Turn ON the ignition, with the engine OFF.
3. Connect a test lamp between the ignition 1 voltage circuit of the MAF sensor and a good ground. Refer to Circuit Testing
4. Connect a DMM to the probe of the test lamp and a good ground.
Is the voltage less than the specified value? B+ Go to Step 12
Go to Step 11

Step 11
Test for an intermittent and for a poor connection at the MAF sensor. Refer to Testing for Intermittent and Poor Connections and Connector Repairs in Wiring Systems.
Did you find and correct the condition? -- Go to Step 14
Go to Step 13

Step 12
Repair the high resistance in the ignition 1 voltage circuit of the MAF sensor. Refer to Wiring Repairs in Wiring Systems.
Did you complete the repair? -- Go to Step 14
--
Step 13
Replace the MAF/IAT sensor. Refer to Mass Air Flow (MAF)/Intake Air Temperature (IAT) Sensor Replacement .
Did you complete the replacement? -- Go to Step 14
--
Step 14
1. Clear the DTCs with a scan tool.
2. Turn OFF the ignition for 30 seconds.
3. Start the engine.
4. Operate the vehicle within the Conditions for Running the DTC. You may also operate the vehicle within the conditions that you observed from the Freeze Frame/Failure Records.
Did the DTC fail this ignition? -- Go to Step 2
Go to Step 15

Step 15
Observe the Capture Info with a scan tool.
Are there any DTCs that have not been diagnosed? -- Go to Diagnostic Trouble Code (DTC) List
System OK



Bill

tblu92

Having the engine die when coming to a stop in-gear or while in P/N is a common problem with heavily modded or camed engines--
Usually fixes are: take out a % from the "throttle follower" in gear & P/N if needed -Start with 10% If you went too far you'll get a hanging idle or a criuse control effect
Add a % to the ' desired airflow" table--In gear & in P/N if needed -Start with 7%--Again if you went to far you'll get a hanging idle or cruise control effect

After the 1.8 rockers and the catback--chances are your fuel trims are way off--I would have them checked and re-calibrated if needed via the MAF frq. table- get them close to "0" or slightly negative--Code p0101 will eventually put your car in a reduced power mode after so many drive cycles--Did you take the MAF screen out? If it came with one and you took it out--that will cause havoc with the fuel trims

DefenderC5

Thanks Bill! I wasn't aware it differed between the years. You have some great information to lend us.

Dreams190

well I went to Horsepower Sales today and spoke with Roger, turns out my fuel trim has caught up with me and the 1.8 rockers


so instead of fixing the tune now, then doing the cam later and paying for another tune.... this is gonna be the excuse I need to do the cam now and only pay for 1 tune...



Thanks for the info guys!!