ECU module replacement

So according to Daewoo, if it see's a 68F degree variation from 190F it will light the MIL and set the code. I know on mine it seemed more touchy than a 68F swing, it was more like a 10F degree swing tripped the light, but I hope this helps. So if you see this swing of temps on your gauge then you can go from there.

"The ECM detects a 20°C (68°F) difference between the ECT sensor and the thermostat regulated
temperature."

Once the issue is fixed, it will turn out the MIL on it's own, so you won't have to reset the monitor tests for inspection.

" The control module turns OFF the malfunction indicator lamp (MIL) after 3 consecutive
ignition cycles that the diagnostic runs and does not fail."

First of all thank you . My daughter just came by with the car fully warmed up with outside air temp of 15'. The 195' thermostat installed yesterday had the engine running at 192' -196' . The code for low temp is not on ( it was running at 189' with old thermostat and taking 3-4 days of driving before throwing low temp code) at this time . We'll see in 3-4 days ?? But now a new old problem is back . The code PO137 bank 1 sensor 2 is on along with check engine light . I had this code gone before by replacing #1 O2 sensor with a genuine AC Delco sensor . I still have a universal O2 sensor in the #2 position . Maybe replace the #2 universal with a genuine AC Delco next ?

Here is an attempt at a paste of the TIS for P0137 in case it helps.

I hope it works! lol
==========================================


2004 Chevrolet Aveo |
Aveo (VIN S)
Service Manual | Document ID: 1483995

---

DTC P0137


Circuit Description


The engine control module (ECM) supplies a voltage near 450 mV between the
heated oxygen sensor (HO2S) high signal circuit and the low reference circuit.
The HO2S varies the voltage over a range from about 1,000 mV when the exhaust is
rich, down through about 10 mV when the exhaust is lean.

The ECM monitors and stores the HO2S voltage information. The ECM evaluates
the HO2S voltage samples in order to determine the amount of time that the HO2S
voltage was out of range. The ECM compares the stored HO2S voltage samples taken
within each sample period and determines if the majority of the samples are out
of the operating range.

The ECM monitors the HO2S voltage for being fixed below a predetermined
voltage. If the ECM detects the voltage is too low, this DTC sets.

The HO2S utilizes the following circuits:

•	A signal circuit

•	A low reference circuit

•	An ignition 1 voltage circuit

•	A heater control circuit

DTC Descriptor


This diagnostic procedure supports the following DTC:

DTC P0137 HO2S Circuit Low Voltage Sensor 2

Conditions for Running the DTC


Closed Loop Test

•	DTCs P0106, P0107, P0108, P0117, P0118, P0122, P0123, P0141, P0171, P0172, P0201-P0204, P0300, P0336, P0337, P0351, P0352, P0401, P0402, P0404, P0405, P0406, P0441, P0443, P0488, P0502, P0506, and P0507 are not set.

•	The engine coolant temperature is more than 60°C (140°F).

•	The ignition 1 voltage is more than 10 volts.

•	The calculated airflow is more than 9 g/s.

•	The fuel system is in closed loop.

•	DTC P0137 runs continuously once the above conditions are met for 3 seconds.

Power Enrichment Test

•	DTCs P0106, P0107, P0108, P0117, P0118, P0122, P0123, P0141, P0171, P0172, P0201-P0204, P0300, P0336, P0337, P0351, P0352, P0401, P0402, P0404, P0405, P0406, P0441, P0443, P0488, P0502, P0506, and P0507 are not set.

•	The engine coolant temperature is more than 60°C (140°F).

•	The ignition 1 voltage is more than 10 volts.

•	The air fuel ratio is less than or equal to 13.5:1.

•	DTC P0137 runs continuously once the above conditions are met for 3 seconds.

Conditions for Setting the DTC


Closed Loop Test

•	The ECM detects that the HO2S 2 voltage is less than 52 mV.

•	The condition exists for more than 4 minutes.

Power Enrichment Test

•	The ECM detects that the HO2S 2 voltage is less than 35 mV during power enrichment.

•	The condition exists for more than 11 seconds.

Action Taken When the DTC Sets

•	The control module illuminates the malfunction indicator lamp (MIL) when the diagnostic runs and fails.

•	The control module records the operating conditions at the time the diagnostic fails. The control module stores this information in the Freeze Frame/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.

[TABLE="width: 95%"]

[TH="align: center"]Step
[/TH]
[TH="align: center"]Action
[/TH]
[TH="align: center"]Values
[/TH]
[TH="align: center"]Yes
[/TH]
[TH="align: center"]No
[/TH]


[TD="colspan: 5, align: left"]Schematic Reference: Engine
Controls Schematics

Connector End View Reference: Engine
Control Module Connector End Views or Engine
Controls Connector End Views
[/TD]


[TD="align: center"]1
[/TD]
[TD="align: left"]Did you perform the Diagnostic System Check - Engine Controls?
[/TD]
[TD="align: center"]--
[/TD]
[TD="align: center"]Go to Step 2
[/TD]
[TD="align: center"]Go to Diagnostic
System Check - Engine Controls
[/TD]


[TD="align: center"]2
[/TD]

1. Start the engine.
2. Allow the engine to reach the normal operating temperature.
3. Operate the engine above 1,200 RPM for 30 seconds and then allow the
   engine to idle.
4. Observe the HO2S 2 voltage parameter with a scan tool.

Is the voltage less than the specified value?
[TD="align: center"]52 mV
[/TD]
[TD="align: center"]Go to Step 4
[/TD]
[TD="align: center"]Go to Step 3
[/TD]


[TD="align: center"]3
[/TD]
[TD="align: left"]

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?[/TD]
[TD="align: center"]--
[/TD]
[TD="align: center"]Go to Step 4
[/TD]
[TD="align: center"]Go to Intermittent
Conditions
[/TD]


[TD="align: center"]4
[/TD]

1. Turn OFF the ignition.
2. Disconnect the heated oxygen sensor (HO2S) 2.
3. Start the engine.
4. Observe the HO2S 2 voltage parameter with a scan tool.

Is the voltage within the specified range?
[TD="align: center"]350-550 mV
[/TD]
[TD="align: center"]Go to Step 6
[/TD]
[TD="align: center"]Go to Step 5
[/TD]


[TD="align: center"]5
[/TD]
[TD="align: left"]Test the signal circuit of the HO2S 2 for a short to ground. Refer to Circuit
Testing and Wiring
Repairs in Wiring Systems.

Did you find and correct the condition?
[/TD]
[TD="align: center"]--
[/TD]
[TD="align: center"]Go to Step 11

[/TD]
[TD="align: center"]Go to Step 8
[/TD]

[TR]
[TD="align: center"]6
[/TD]

Test or inspect for the following conditions:

•

[TD="align: center"]7

	Lean fuel injectors--Refer to Fuel Injector Balance Test with Special Tool .
•	Low fuel system pressure--Refer to Fuel System Diagnosis .
•	Fuel that is contaminated--Refer to Alcohol/Contaminants-in-Fuel Diagnosis .
•	Exhaust leaks near the HO2S--Refer to Symptoms - Engine Exhaust .
•	Engine vacuum leaks

[TD="align: center"]--
[/TD]
[TD="align: center"]Go to Step 11

[/TD]
[TD="align: center"]Go to Step 9
[/TD]


[TD="align: center"]8
[/TD]

[TD="align: center"]--
[/TD]
[TD="align: center"]Go to Step 11

[/TD]
[TD="align: center"]Go to Step 10

[/TD]


[TD="align: center"]9
[/TD]

[TD="align: center"]--
[/TD]
[TD="align: center"]Go to Step 11

[/TD]
[TD="align: center"]--
[/TD]


[TD="align: center"]10
[/TD]

[TD="align: center"]--
[/TD]
[TD="align: center"]Go to Step 11

[/TD]
[TD="align: center"]--
[/TD]


[TD="align: center"]11
[/TD]

[TD="align: center"]--
[/TD]
[TD="align: center"]Go to Step 2
[/TD]
[TD="align: center"]Go to Step 12

[/TD]


[TD="align: center"]12
[/TD]

[TD="align: center"]--
[/TD]
[TD="align: center"]Go to Diagnostic
Trouble Code (DTC) List
[/TD]
[TD="align: center"]System OK
[/TD]

Test for an intermittent and poor connections at the harness connector of the HO2S 2. Refer to Testing for Intermittent Conditions and Poor Connections and Connector Repairs in Wiring Systems. Did you find and correct the condition?

Test for an intermittent and poor connection at the engine control module (ECM). Refer to Testing for Intermittent Conditions and Poor Connections and Repairing Connector Terminals in Wiring Systems. Did you find and correct the condition?

Replace the HO2S 2. Refer to Heated Oxygen Sensor 2 Replacement . Did you complete the replacement?

Replace the ECM. Refer to Engine Control Module Replacement . Did you complete the replacement?

Clear the DTCs with a scan tool. Turn OFF the ignition for 30 seconds. Start the engine. 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?

Observe the Capture Info with a scan tool. Are there any DTCs that have not been diagnosed?

My head is spinning with all the information . Part of my problem , aside from being a dinosaur , is that I only have access to the vehicle briefly ( it's used everyday at another address) . I do appreciate all your help . I think if the temp code doesn't come back in 3-4 days of commuting I'll consider it ( the low temp problem ) fixed and that the ECU is not bad . If the ECU isn't bad I'll take a chance that the other ( #2 downstream ) universal O2 sensor is the problem and change it out for a genuine AC Delco . ( I did that on #1 upstream O2 sensor when it was throwing the O2 code I replaced the universal with a AC Delco and it fixed it )
Will post my results in a week or two ??? and hopefully someone else can learn from my experience.

QUICK QUESTION ???? Bank 1 Sensor 2 . Does that , I hope , mean the O2 sensor after the cat ????

Wow that made a mess! So much for my copy and paste ability. Wont be trying that again.

Yes sensor 2 is the downstream unit behind the cat, if my memory serves me correct.

Quote:

---

Originally Posted by 06T200

Wow that made a mess! So much for my copy and paste ability. Wont be trying that again.

Yes sensor 2 is the downstream unit behind the cat, if my memory serves me correct.

---

Latest update : It's been four days of driving and Low Temp code hasn't come back on . You guys were right the

high temp thermostat cured the touchy ECU . 189' wasn't enough now it's 196' and okay . THANKS : )

Now the #2 after Cat O2 sensor code keeps coming on . Moral of the story ....DON'T TRUST UNIVERSAL O2 SENSORS . First #1 Universal O2 went out , replaced with genuine AC Delco . All fixed . Now will replace #2 O2 Universal sensor with genuine part and that should cure Check Engine Light problem .

never trust universal o2 sensors in these newer cars, just because an o2 has a range close to matching what your car expects, does not mean that it will work 100%. I would only do a direct replacement (not necessarily genuine OEM, but wired for plug in for my car) to replace an o2. That narrows the closeness of the range and means the o2 is more likely to work.

Glad you didn't need an ECU.

I learn lots of things the hard way ; / but once learned that way I never forget : )


I do have a question , how can sellers on ebay want $44 to $344 for the same ??????? ac delco O2 sensors ? It's an amazing price range . Plus some universal (already wired to plug) are as low as $15. ( For the #1 AC Delco O2 sensor I paid $140. from a Authorized Chevy dealer but he only had one for sale on ebay otherwise I'd order from him again )

Have you checked rockauto? They had the NTK (OE) unit a couple of months ago, there is one listed on the site that indicates it is 'downstream' or 'upstream' for $50. But I thought they were different so this is a bit confusing. I have only replaced the upstream unit.

Glad the temp error has gone away, almost there!