P0121 code
05-28-2017 | 09:28 PM
#2
Moderator
Joined: 01-23-2009
Posts: 25,339
From: Fredericksburg,VA
This link: https://www.obd-codes.com/p0121 is very different from what the HHR Service Manual says.
Mitchell OnDemand says that you should be looking for air getting into the manifold between the MAF and the MAP. Perhaps a malfunction of either the MAP or MAF.
Most likely the MAP is malfunctioning or a vacuum leak on the manifold
What they are saying is : it's not a problem with the throttle position sensor, it's a problem with what the sensor is sensing. I.E.: more airflow than expected.
On a 2006 I would inspect the rubber air horn, especially where the PCV hose attached, for cracks. Or the power brake booster vacuum line. Might even indicate a bad brake booster.
Another possibility is a bad connection at one of the connectors to the ECM.
Mitchell OnDemand says that you should be looking for air getting into the manifold between the MAF and the MAP. Perhaps a malfunction of either the MAP or MAF.
Most likely the MAP is malfunctioning or a vacuum leak on the manifold
What they are saying is : it's not a problem with the throttle position sensor, it's a problem with what the sensor is sensing. I.E.: more airflow than expected.
On a 2006 I would inspect the rubber air horn, especially where the PCV hose attached, for cracks. Or the power brake booster vacuum line. Might even indicate a bad brake booster.
Another possibility is a bad connection at one of the connectors to the ECM.
05-29-2017 | 07:30 AM
#3
Thread Starter
Member
Joined: 04-04-2015
Posts: 37
From: Old Monroe, MO
This link: https://www.obd-codes.com/p0121 is very different from what the HHR Service Manual says.
Mitchell OnDemand says that you should be looking for air getting into the manifold between the MAF and the MAP. Perhaps a malfunction of either the MAP or MAF.
Most likely the MAP is malfunctioning or a vacuum leak on the manifold
What they are saying is : it's not a problem with the throttle position sensor, it's a problem with what the sensor is sensing. I.E.: more airflow than expected.
On a 2006 I would inspect the rubber air horn, especially where the PCV hose attached, for cracks. Or the power brake booster vacuum line. Might even indicate a bad brake booster.
Another possibility is a bad connection at one of the connectors to the ECM.
Mitchell OnDemand says that you should be looking for air getting into the manifold between the MAF and the MAP. Perhaps a malfunction of either the MAP or MAF.
Most likely the MAP is malfunctioning or a vacuum leak on the manifold
What they are saying is : it's not a problem with the throttle position sensor, it's a problem with what the sensor is sensing. I.E.: more airflow than expected.
On a 2006 I would inspect the rubber air horn, especially where the PCV hose attached, for cracks. Or the power brake booster vacuum line. Might even indicate a bad brake booster.
Another possibility is a bad connection at one of the connectors to the ECM.
05-29-2017 | 08:39 AM
#4
Moderator
Joined: 01-23-2009
Posts: 25,339
From: Fredericksburg,VA
"shop put on an aluminum intake"; The book says the manifold gaskets are prime suspects. Aluminum is more rigid than plastic, so I'm thinking you may need thicker O-rings on the TB and the head.
I would not trust that shop with DTCs. They completely mis read the description and didn't read the definition. The code descriptor is: Throttle Position Sensor PERFORMANCE. The condition for setting the code is: The ECM detects that the calculated airflow rate is more than expected.
There is not so much air that the ECM can't adjust for it, so you don't get P0171/P0172 lean condition. But it is more than the TP is indicating.
I would not trust that shop with DTCs. They completely mis read the description and didn't read the definition. The code descriptor is: Throttle Position Sensor PERFORMANCE. The condition for setting the code is: The ECM detects that the calculated airflow rate is more than expected.
There is not so much air that the ECM can't adjust for it, so you don't get P0171/P0172 lean condition. But it is more than the TP is indicating.
05-29-2017 | 08:53 AM
#5
Thread Starter
Member
Joined: 04-04-2015
Posts: 37
From: Old Monroe, MO
"shop put on an aluminum intake"; The book says the manifold gaskets are prime suspects. Aluminum is more rigid than plastic, so I'm thinking you may need thicker O-rings on the TB and the head.
I would not trust that shop with DTCs. They completely mis read the description and didn't read the definition. The code descriptor is: Throttle Position Sensor PERFORMANCE. The condition for setting the code is: The ECM detects that the calculated airflow rate is more than expected.
There is not so much air that the ECM can't adjust for it, so you don't get P0171/P0172 lean condition. But it is more than the TP is indicating.
I would not trust that shop with DTCs. They completely mis read the description and didn't read the definition. The code descriptor is: Throttle Position Sensor PERFORMANCE. The condition for setting the code is: The ECM detects that the calculated airflow rate is more than expected.
There is not so much air that the ECM can't adjust for it, so you don't get P0171/P0172 lean condition. But it is more than the TP is indicating.
05-29-2017 | 09:51 AM
#6
Moderator
Joined: 01-23-2009
Posts: 25,339
From: Fredericksburg,VA
Idle relearn is just idling for 4 minutes.
What have you done to change the way the injectors work? What other engine mods?
The pedal controls the air, the ECM controls the fuel. Sound like the person tuning does not know enough.
My guess is you are getting bad MPG.
Have you looked at the EVAP purge valve? Disconnect it completely and blow through it; if it is free flowing it is bad and admitting unmetered air. It can cause P0171/P0172.
Since your car is not stock it is very difficult to diagnose on the interwebs.
What have you done to change the way the injectors work? What other engine mods?
The pedal controls the air, the ECM controls the fuel. Sound like the person tuning does not know enough.
My guess is you are getting bad MPG.
Have you looked at the EVAP purge valve? Disconnect it completely and blow through it; if it is free flowing it is bad and admitting unmetered air. It can cause P0171/P0172.
Since your car is not stock it is very difficult to diagnose on the interwebs.
05-29-2017 | 10:19 AM
#7
Thread Starter
Member
Joined: 04-04-2015
Posts: 37
From: Old Monroe, MO
Idle relearn is just idling for 4 minutes.
What have you done to change the way the injectors work? What other engine mods?
The pedal controls the air, the ECM controls the fuel. Sound like the person tuning does not know enough.
My guess is you are getting bad MPG.
Have you looked at the EVAP purge valve? Disconnect it completely and blow through it; if it is free flowing it is bad and admitting unmetered air. It can cause P0171/P0172.
Since your car is not stock it is very difficult to diagnose on the interwebs.
What have you done to change the way the injectors work? What other engine mods?
The pedal controls the air, the ECM controls the fuel. Sound like the person tuning does not know enough.
My guess is you are getting bad MPG.
Have you looked at the EVAP purge valve? Disconnect it completely and blow through it; if it is free flowing it is bad and admitting unmetered air. It can cause P0171/P0172.
Since your car is not stock it is very difficult to diagnose on the interwebs.
05-29-2017 | 10:38 AM
#9
Administrator
Joined: 10-13-2011
Posts: 37,829
From: Welland,Ont Canada
The system is off Bob from GDZHHR
https://www.chevyhhr.net/forums/feat...mission-51436/
These photos could explain some damages
https://www.chevyhhr.net/forums/feat...mission-51436/
These photos could explain some damages
05-29-2017 | 10:57 AM
#10
Senior Member
Joined: 09-16-2013
Posts: 1,408
From: Tampa, Florida
Once you start putting aftermarket parts on you start getting aftermarket problems. You have done far too many modifications for your issues to be solved by conventional means. Every layer of mod is another potential failure point, unfortunately.
When it comes to cars you can have two of the following, never all three; CHEAP, RELIABLE, FAST
When it comes to cars you can have two of the following, never all three; CHEAP, RELIABLE, FAST