Code 44
- Thread starter mickdowd
- Start date
teamzr1
Supporting vendor
CODE 44 - Lean Exhaust
Trouble Code 44 indicates that the O2 sensor is showing a persistently high exhaust oxygen content (lean),
despite the efforts of the ECM to increase injector on-time (thus increasing fuel delivered).
Integrator and BLM numbers may indicate > 128 by a substantial margin.
Really is best to obtain or find someone with an OBDI scanner to focus into what the cause is
With scanner, determine if in fact the BLMs are reporting lean OR the O2 sensor is faulty or some type of air or exhaust leak
How old are the O2 sensors, suspect them if over 40,000 miles on them
At idle with engine warned up the O2s should report about 0.500 mVolts as that would be about a 14:7.1 AFR
The conditions for setting this code are:
Follow these :
1) O2 sensor defective or wires defective
2) Lean injectors (dirty or blocked)
3) Water in fuel
4) Exhaust leaks upstream of O2 sensor
5) Fuel pressure or volume too low
6) MAF sensor reading lower airflow than is actually present
7) Vacuum leaks
8) Incorrect or poorly calibrated PROM in the ECM
Trouble Code 44 indicates that the O2 sensor is showing a persistently high exhaust oxygen content (lean),
despite the efforts of the ECM to increase injector on-time (thus increasing fuel delivered).
Integrator and BLM numbers may indicate > 128 by a substantial margin.
Really is best to obtain or find someone with an OBDI scanner to focus into what the cause is
With scanner, determine if in fact the BLMs are reporting lean OR the O2 sensor is faulty or some type of air or exhaust leak
How old are the O2 sensors, suspect them if over 40,000 miles on them
At idle with engine warned up the O2s should report about 0.500 mVolts as that would be about a 14:7.1 AFR
The conditions for setting this code are:
- no Code 33 or Code 34 (MAF Error) present, and
- the O2 sensor voltage remains below 250 mVolts, and
- the ECM is in Closed Loop control, and
- the above conditions exist for more than 50 seconds.
Follow these :
1) O2 sensor defective or wires defective
2) Lean injectors (dirty or blocked)
3) Water in fuel
4) Exhaust leaks upstream of O2 sensor
5) Fuel pressure or volume too low
6) MAF sensor reading lower airflow than is actually present
7) Vacuum leaks
8) Incorrect or poorly calibrated PROM in the ECM
Thank you again team zr1. You are a font of knowledge.
teamzr1
Supporting vendor
You're Welcome
What year is you C4 and which engine ?
If engine is running way lean, I would not suggest you allow engine to run high RPMs and engine loads
as that will induce a lot of engine knock
I would need more info to point you to where problem could be but follow punch list above
If I recall
Part number for front 02 sensors for the C4 from AcDelco is
AFS75 ( which says how long the wires are in mm )
GM part number 19178930
What year is you C4 and which engine ?
If engine is running way lean, I would not suggest you allow engine to run high RPMs and engine loads
as that will induce a lot of engine knock
I would need more info to point you to where problem could be but follow punch list above
If I recall
Part number for front 02 sensors for the C4 from AcDelco is
AFS75 ( which says how long the wires are in mm )
GM part number 19178930
teamzr1
Supporting vendor
Is it possible the gas in it is bad or the wrong type ?
When the engine is cold that is called "Open Loop" the ECM (engine controller) ignores the feedback reporting sensors like
the MAF, O2 sensors, etc and uses predicted airmass values in the ECM
Being RPMs are random when engine is warm, that is called "closed Loop" and the ECM then is adjusting as the sensors
as to what they are reporting
As my list above, could be the MAF is dirty, some unmetered air leak between the MAF and throttlebody,
Some vacuum leak, fuel injectors dirty, clogged, fuel pressure too low at idle, etc
When the engine is cold that is called "Open Loop" the ECM (engine controller) ignores the feedback reporting sensors like
the MAF, O2 sensors, etc and uses predicted airmass values in the ECM
Being RPMs are random when engine is warm, that is called "closed Loop" and the ECM then is adjusting as the sensors
as to what they are reporting
As my list above, could be the MAF is dirty, some unmetered air leak between the MAF and throttlebody,
Some vacuum leak, fuel injectors dirty, clogged, fuel pressure too low at idle, etc
Thank you for your help so far. The C4 has been at the American Auto Centre in Minworth for 8 weeks. I collected it back yesterday. The bill was £1180. I have got it home and it is exactly the same. When warm it ticks over between 300 and 1200 rpm. I am at my wits end with it. I checked with the paperclip and it is showing codes 33 and 44. The idle air control has been replaced, also 2 off ry109 relays and a lxe6 esc control. Any help would be massively appreciated. I paid 14k for the car. It is mint in every other way.
teamzr1
Supporting vendor
What the frick *&^% is that 
They keep the C4 for 2 whole months, charge 1180 bucks and the same problem exists, I'd burn the joint down !
You still have not mentioned what year, model and engine, as my answers change depending on that
Anyone that works on GM vehicles should have an OBD-I scanner and would find out what the problem is at idle in closed loop
in 5 minutes or less.
As I posted above the code 44 says the O2 sensor is reporting that the AFR is very lean, the scanner would show if that is true or not as at idle the AFR should be 14.7:1, any higher than that would be lean, if not having OBD-I scanner than an exhaust analyzer stuck in an exhaust tip would read what the AFR is
Code 33, depending on which year C4 and which engine so that code would mean either a MAP sensor reports low vacuum or
The MAF sensor is not reporting the amount of airflow correctly
Typical causes for these codes include:
1) Faulty MAF-to-ECM connection
2) Exceedingly noisy spark plug wires
3) Poor routing of MAF harness (i.e. near coil packs)
4) Maladjusted TPS sensor
5) Defective MAF sensor
6) Defective ECM
7) Defective MAP sensor, or vacuum leak
As to MAF which mounts between the air cleaner and throttle body, has it been cleaned with MAF cleaner ?
And is the aircleaner clean ?
Using a carb spray cleaner spray around hoses, intake manifold, etc and if there is a leak that spray would get sucked in
and the RPMs would quickly change
#4 above if TPS sensor which is mounted off the throttlebody is out of adjustment, should be checked and adjusted if needed
They keep the C4 for 2 whole months, charge 1180 bucks and the same problem exists, I'd burn the joint down !
You still have not mentioned what year, model and engine, as my answers change depending on that
Anyone that works on GM vehicles should have an OBD-I scanner and would find out what the problem is at idle in closed loop
in 5 minutes or less.
As I posted above the code 44 says the O2 sensor is reporting that the AFR is very lean, the scanner would show if that is true or not as at idle the AFR should be 14.7:1, any higher than that would be lean, if not having OBD-I scanner than an exhaust analyzer stuck in an exhaust tip would read what the AFR is
Code 33, depending on which year C4 and which engine so that code would mean either a MAP sensor reports low vacuum or
The MAF sensor is not reporting the amount of airflow correctly
Typical causes for these codes include:
1) Faulty MAF-to-ECM connection
2) Exceedingly noisy spark plug wires
3) Poor routing of MAF harness (i.e. near coil packs)
4) Maladjusted TPS sensor
5) Defective MAF sensor
6) Defective ECM
7) Defective MAP sensor, or vacuum leak
As to MAF which mounts between the air cleaner and throttle body, has it been cleaned with MAF cleaner ?
And is the aircleaner clean ?
Using a carb spray cleaner spray around hoses, intake manifold, etc and if there is a leak that spray would get sucked in
and the RPMs would quickly change
#4 above if TPS sensor which is mounted off the throttlebody is out of adjustment, should be checked and adjusted if needed
Thank you so much for that.What the frick *&^% is that
They keep the C4 for 2 whole months, charge 1180 bucks and the same problem exists, I'd burn the joint down !
You still have not mentioned what year, model and engine, as my answers change depending on that
Anyone that works on GM vehicles should have an OBD-I scanner and would find out what the problem is at idle in closed loop
in 5 minutes or less.
As I posted above the code 44 says the O2 sensor is reporting that the AFR is very lean, the scanner would show if that is true or not as at idle the AFR should be 14.7:1, any higher than that would be lean, if not having OBD-I scanner than an exhaust analyzer stuck in an exhaust tip would read what the AFR is
Code 33, depending on which year C4 and which engine so that code would mean either a MAP sensor reports low vacuum or
The MAF sensor is not reporting the amount of airflow correctly
Typical causes for these codes include:
1) Faulty MAF-to-ECM connection
2) Exceedingly noisy spark plug wires
3) Poor routing of MAF harness (i.e. near coil packs)
4) Maladjusted TPS sensor
5) Defective MAF sensor
6) Defective ECM
7) Defective MAP sensor, or vacuum leak
As to MAF which mounts between the air cleaner and throttle body, has it been cleaned with MAF cleaner ?
And is the aircleaner clean ?
Using a carb spray cleaner spray around hoses, intake manifold, etc and if there is a leak that spray would get sucked in
and the RPMs would quickly change
#4 above if TPS sensor which is mounted off the throttlebody is out of adjustment, should be checked and adjusted if needed
teamzr1
Supporting vendor
OK so Code 33 is definitely a MAF related issue in 85-89 with L98
and not a MAP issue
Clean the MAF, with a MAF cleaner only, make sure no air leaks from aircleaner to the throttlebody and that the wiring to MAF is good and pins are clean
And as I mentioned,
Check the TPS sensor reading at base idle (450rpm) and at WOT position.
Can be done via OBD-I scanner or a multi meter set to low D/C voltage
With ign key on, engine off, TPS should show about 0.450 mVolts and when gas pedal to floor 5 volts
The TPS screw mount, one side is slotted, loosen screws of TPS and not on the gas pedal adjust for that 0.450 mVolt
and then hard on gas pedal should be the 5 volts
and not a MAP issue
Clean the MAF, with a MAF cleaner only, make sure no air leaks from aircleaner to the throttlebody and that the wiring to MAF is good and pins are clean
And as I mentioned,
Check the TPS sensor reading at base idle (450rpm) and at WOT position.
Can be done via OBD-I scanner or a multi meter set to low D/C voltage
With ign key on, engine off, TPS should show about 0.450 mVolts and when gas pedal to floor 5 volts
The TPS screw mount, one side is slotted, loosen screws of TPS and not on the gas pedal adjust for that 0.450 mVolt
and then hard on gas pedal should be the 5 volts
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teamzr1
Supporting vendor
That really pisses me off, to no end, hell if I had that amount of free money I could get laid
Or a whole new set of sticky tires
With the electronics, these cars have a simple use of OBD-II scanner would push the nose of the tech as which sensor is reporting an issue and the
if the fuel injectors are commanded to lean or not, how the MAF was functioning and reporting correct amount of airmass
UK really has a business case of getting a GM expert who knows what the hell OBD-I and II is all about
Steven Smith
CCCUK Member
Is this the same car that you were looking for an engine rebuild in September?
Steven Smith
CCCUK Member
teamzr1
Supporting vendor
With engine warmed up and ECM has gone into "Closed Loop" if not having an OBD-I scanner
Then using a good D/C meter
O2 sensors used are "Narrow Band" that function from 0 to 1 Volt (1,000 mVolt)
At idle, output of O2 sensor should be around 0.500 mVolt,
The higher the value reads above that, the richer the AFR is,
Lower values equals, leaner it is
So if the DTC trips says O2 reporting lean values, then should read values below 0.500 mVolts
Then using a good D/C meter
O2 sensors used are "Narrow Band" that function from 0 to 1 Volt (1,000 mVolt)
At idle, output of O2 sensor should be around 0.500 mVolt,
The higher the value reads above that, the richer the AFR is,
Lower values equals, leaner it is
So if the DTC trips says O2 reporting lean values, then should read values below 0.500 mVolts