It would seem so!

We have these codes, that seem to haunt us. our family car is extremely unreliable, and it just started recently. The codes we are getting are: P0521, P2135, P0121.

After replacing the TB, checking the harness, and replacing harness to the Crankshaft sensor (stripped wire)...after putting in a new PS pump, we are just pulling our hair and trying to think what it could be?

The car seems to hesitate randomly while driving in mostly all gears, and it will randomly pop up Reduced Engine Power, although not very recently.

The throttle body we replaced was a Cardone Reman, so I am not blind to having bad reman products but its really weird.

 

Year? Engine?

 

Sorry, its a 2007 Chevy Impala Police 3.9.... Pulled the codes again today after reset and same 3 codes. Again we just replaced the TB with a cardone Reman, but its under warranty for a year.

I do notice it is VERy intermittent, does not happen every time I start to drive. It seems however to stumble or lag when driving on the roadway like loss of power, its not smooth as it was.

 

<DL><DT>Circuit/System Verification</DT><DD>

1. If DTC P0641 or P0651 is set, refer to DTC P0641 or P0651.
2. Ignition ON, observe the scan tool TP sensor 1 voltage parameter. The reading should be between 4.75–0.35 volts and change with accelerator pedal input.
3. Ignition ON, observe the scan tool TP sensor 2 voltage parameter. The reading should be between 0.25–4.59 volts and change with accelerator pedal input.
4. Ignition ON, observe the scan tool TP sensor 1 and 2 parameter. The scan tool should indicate agree.
5. Clear the DTCs with the scan tool. Operate the vehicle within the Conditions for Running the DTC, or within the conditions that you observed from the Freeze Frame/Failure Records.
6. Verify that DTC P0120 or P0220 are not the only throttle position DTCs set.
   • If DTC P0120 or P0220 are the only DTCs set, replace the control module.
7. If the vehicle passes the Circuit/System Verification test, operate the vehicle within the Conditions for running the DTC. You may also operate the vehicle within the conditions that are captured in the Freeze Frame/Failure Records list.

</DD></DL><DL><DT>Circuit/System Testing</DT><DD>

1. Ignition OFF, disconnect the harness connector at the throttle body.
2. Ignition OFF for 90 seconds, test for less than 5 ohms of resistance between the low reference circuit terminal C and ground.
   • If greater than 5 ohms, test the low reference circuit for an open/high resistance. If the circuit tests normal, replace the ECM.
3. Ignition ON, test for 4.8–5.2 volts between 5-volt reference circuit terminal E and ground.
   • If less than 4.8 volts, test 5-volt reference circuit for a short to ground or an open/high resistance. If the circuit tests normal, replace the ECM.
   • If greater than 5.2 volts, test the 5-volt reference circuit for a short to voltage. If the circuit tests normal, replace the ECM.
4. Verify the scan tool TP sensor 1 voltage is less than 0.1 volt.
   • If greater than 0.1 volt, test the signal circuit terminal D for a short to voltage. If the circuit tests normal, replace the ECM.
5. verify the scan tool TP sensor 2 voltage is greater than 4.8 volts.
   • If less than 4.8 volts, test the signal circuit for a short to ground. If the circuit tests normal, replace the ECM.
6. Install a 3A fused jumper wire between the signal circuit terminal D and the 5-volt reference circuit terminal E of the TP sensor 1. Verify the TP sensor 1 voltage is greater than 4.8 volts.
   • If less than 4.8 volts, test the TP sensor 1 signal circuit for a short to ground or an open/high resistance. If the circuit tests normal, replace the ECM.
7. Install a 3A fused jumper wire between the signal circuit terminal F and the low reference circuit terminal C of the TP sensor 2. Verify that the TP sensor 2 voltage is less than 0.1 volt.
   • If greater than 1.0 volt, test the TP sensor 2 signal circuit for a short to voltage or an open/high resistance. If the circuit tests normal, replace the ECM.
8. Ignition OFF for 90 seconds, disconnect the harness connector at the ECM.
9. Test for less than 5 ohms of resistance on all TP sensor circuits between the following terminals:
   • ECM C2 signal circuit terminal 65 (64 for U van) to TP terminal D
   • ECM C2 signal circuit terminal 63 (66 for U van) to TP terminal F
   • ECM C2 5-volt reference circuit terminal 3 (44 for U van) to terminal E
     • If greater than 5 ohms, repair the affected circuit for open/high resistance.
10. Test for infinite resistance between TP sensor 1 signal circuit terminal D and TP sensor signal circuit terminal F.
    • If less than infinite resistance, repair the short between TP sensor 1 signal circuit and TP sensor 2 signal circuit.
11. If all circuits test normal, replace the throttle body.

</DD></DL>This is for the P2135 code. I'm sure if you find this problem it will also repair the P0121. The P0521 is for your engine oil pressure sensor performance.

 

What's the engine mileage?

This excellent summarization by the prior poster is valid, unless the

engine has severe wear, extremely high mileage, or some other issue which

is also tripping the sensors.

The testing and troubleshooting method assumes no major vacuum leaks,

oil, or antifreeze leaks, all basic maintenance is complete, and the negative

cable, engine to firewall ground-strap, and positive battery cable haven't

been compromised. Assumes also spark plugs and wires are good. It's been

my sad experience that "100k" Iridium plugs are good to 50k, and a change in

plug wires, at this point, may be in order, to avoid arcing to the block.

In the event, of course, that all tests and procedures in post #4 don't

produce...

 

Its a 2007 Chevy Impala POLICE w/ 3.9 gas.

It has 126,000 miles.