ECU module replacement

[old n' slow]

Called the local garage this morning . He must have talked to you guys He looked at the car yesterday and went online last night to research problem . He thinks it needs a higher temp thermostat (or the new one isn't quite doing it's job)
Something I should have just done myself but at least I didn't go ordering a new expensive ECU just to find it didn't solve problem.
After a few days of driving we'll see if that solves the problem and I will let you all know . Thanks again .

[06T200]

Cool glad it's some help toward a low cost solution. Hmm, you found a sharp mechanic! it's such a cheap item, and I know I tend to overlook the value of some parts. Rabbit is right, the t-stat is not the most accurate critter ever invented, and they do vary enough to tick off the ecm. Hopefully it will save you from the big dollar repairs and get rolling again.

[old n' slow]

Cool glad it's some help toward a low cost solution. Hmm, you found a sharp mechanic! it's such a cheap item, and I know I tend to overlook the value of some parts. Rabbit is right, the t-stat is not the most accurate critter ever invented, and they do vary enough to tick off the ecm. Hopefully it will save you from the big dollar repairs and get rolling again.

The 195' thermostat is in now it's wait a few days to see if the check engine light stays off .

Will report back , thx .

[old n' slow]

Check engine light came back on with the high 195' temperature thermostat installed

On the way to work in 15' temperatures . Next step a new or used ECU gamble .

I sure miss the days of carburetors, points,condensers and coils . Old n' frustrated .

[xintersecty]

Check engine light came back on with the high 195' temperature thermostat installed

I sure miss the days of carburetors, points,condensers and coils . Old n' frustrated .

Rabbit said that he had multiple T-Stats fail before. And I sure don't miss carburetors, points,condensers and coils <- and to that list vacuum advance, flooded engines, and lame smog controls. Nope don't miss them one bit.

[old n' slow]

Rabbit said that he had multiple T-Stats fail before. And I sure don't miss carburetors, points,condensers and coils <- and to that list vacuum advance, flooded engines, and lame smog controls. Nope don't miss them one bit.

In the 60's there were no smog controls and you could fix almost anything on the side of the road : )

Unfortunately the cars back then were apt to leave you on the side of the road more often also : (

[xintersecty]

In the 60's there were no smog controls and you could fix almost anything on the side of the road : )

Unfortunately the cars back then were apt to leave you on the side of the road more often also : (

My 1972 beetle left me on the side of the road more times than my aveo. I really laughed out loud on that one. I really empathize with your issue. A constant nagging code would get to me too. Then again I use a ODBII to bluetooth convertor and a phone app. So I can constantly check for new codes and clear them. As it stands my truck has one now, evap control.

[06T200]

Well that sucks! So the same P0128 came back? If I were you I would at least connect your OBD gauge to see what the temp really is. If it is staying above 190+ then I don't know why it would throw a code. This was how I was able to eyeball the change in engine temps from one t-stat to a new one.

So if you are driving along, and you see the engine temp warm up to the target (195F), you will notice it hover around as the fan cycles or any air passes through the radiator. When I would drive on a flakey t-stat the temps would hover between 172-191, and if the engine temp dropped much below 190 it set the code, sounded the code alarm on my ultraguage and the MIL would be on.

I know the situation old'n slow is in, gotta have it code free for the 'state inspection' lackeys.

If you can tell me the exact code you are now getting on this reset, I can find the TIS document for that code and see what the drill is to troubleshoot it. There is a sheet for each code, but I would need to know if it is the P0128 or if you have a different one, as the process is totally different with each DTC.

[xintersecty]

If you don't have a scanner that publishes codes and you have an android smart phone get this: http://www.amazon.com/iKKEGOL-Blueto.../dp/B00EM8E3HM

This will give you the opportunity to see the info in real time using this program: Torque &mdash; OBD2 Performance and Diagnostics for your Vehicle

[06T200]

I can't post PDF's on here, but if you PM me your email address I can email you the TIS for the P0128 code for 'low coolant temp' that might help you out.

FWIW here is a screen paste of said document. Not sure if this is even readable, but the best I can do outside of email.





2004 ChevroletAveo| Aveo (VIN S)Service Manual| Engine| Engine Controls - 1.6L (L91)| Repair Instructions|
Document ID: 1458885
DTC P0128
Circuit Description
The engine control module (ECM) monitors the temperature of the engine coolant for engine
control and as an enabling criteria for some diagnostics. The amount of air flow into an engine is
proportional to the amount of heat an engine generates. The ECM monitors the amount of air flow
into the engine to calculate engine coolant temperature (ECT). The ECM uses the calculated
temperature to determine if the engine has warmed up to the thermostat regulating temperature.
If the coolant temperature does not increase normally or does not reach regulating temperature of
the thermostat, diagnostics that use the ECT as enabling criteria, may not run when expected. If
the engine coolant temperature fails to reach the thermostat regulating temperature, before a
predetermined amount of air flow enters the engine, this DTC sets.
DTC Descriptor
This diagnostic procedure supports the following DTC:
DTC P0128 Engine Coolant Temperature (ECT) Below Thermostat Regulating Temperature
Conditions for Running the DTC
Conditions for Setting the DTC
The ECM detects a 20°C (68°F) difference between the ECT sensor and the thermostat regulated
temperature.
Action Taken When the DTC Sets
• DTCs P0117, P0118, P0122, P0123, P0502, P0562, P0563, P0606, and U0101 are not set.
• The engine is operating.
• The start-up intake air temperature is more than -39°C (-38°F).
• Before the ECM can report DTC P0128 failed, the engine must be idling for more than a
predetermined amount of time which is based off of start-up coolant temperature.
• Before the ECM can report DTC P0128 failed, theairflow into the engine must be more than a
predetermined amount which is based off of start-up coolant temperature.
• DTC P0128 runs once an ignition cycle once the above conditions are met.
• 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.

Page 1of 4 Document ID: 1458885
Conditions for Clearing the MIL/DTC
Diagnostic Aids
Test Description
The numbers below refer to the step numbers in the diagnostic table.
5. This step tests for excessive resistance in the ECT circuit.
6. This step isolates the condition. If the temperature changes, test for a condition in the low
reference circuit. If the temperature remains the same test the signal circuit for a condition.
• 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.
• Use the J 35616Connector Test Adapter Kit for any test that requires probing the ECM
harness connector or a component harness connector.
• For an intermittent condition, refer to IntermittentConditions.
Step Action Values Yes No
Schematic Reference: EngineControls Schematics
Connector End View Reference: EngineControl Module Connector End Viewsor Engine
Controls Connector End Views
1
Did you perform the Diagnostic System
Check - Engine Controls?
--
Go to Step 2
Go to
Diagnostic
System Check -Engine Controls
2
Is the engine cooling system low on
coolant?
--
Go to Loss of
Coolantin
Engine Cooling Go to Step 3
3
Is the customer's concern that the engine
does not reach operating temperature or
that the heater output is low?
--
Go to
Thermostat
Diagnosisin
Engine Cooling Go to Step 4
4
Important: Return to this diagnostic
procedure after you complete the
thermostat diagnosis.
Test for the correct operation of the
thermostat. Refer to ThermostatDiagnosis
in Engine Cooling.
--
Page 2of 4 Document ID: 1458885
Did you find and correct the condition? Go to Step 13 Go to Step 5
5
1. Turn OFF the ignition.
2. Disconnect the engine coolant
temperature (ECT) sensor.
3. Connect a 3-amp fused jumper wire
between the signal circuitand the low
reference circuit of the ECT sensor.
4. Turn ON the ignition, with the engine
OFF.
5. Observe the ECT sensor parameter
with a scan tool.
Is the temperature more than the specified
value?
214°C
(417°F)
Go to Step 9 Go to Step 6
6
1. Connect a 3-amp fused jumper
between the signal circuit of the ECT
sensor and the engine control
module (ECM) housing.
2. Observe the ECT sensor parameter
with a scan tool.
Is the temperature more than the specified
value?
214°C
(417°F)
Go to Step 7 Go to Step 8
7
Test the low reference circuit of the ECT
sensor for high resistance. Refer to Circuit
Testingand WiringRepairsin Wiring
Systems.
Did you find and correct the condition?
--
Go to Step 13 Go to Step 10
8
Test the signal circuit of the ECT sensor for
high resistance. Refer to CircuitTestingand
WiringRepairsin Wiring Systems.
Did you find and correct the condition?
--
Go to Step 13 Go to Step 10
9
Test for shorted terminals and poor
connections at the ECT sensor. Refer to
Testingfor Intermittent Conditions and
Poor Connectionsand ConnectorRepairsin
Wiring Systems.
Did you find and correct the condition?
--
Go to Step 13 Go to Step 11
10
Test for shorted terminals and poor
connections at the ECM. Refer to Testing
for Intermittent Conditions and Poor
Connectionsand ConnectorRepairsin
Wiring Systems.
Did you find and correct the condition?
--
Go to Step 13 Go to Step 12
11
Replace the ECT sensor. Refer to Engine
Coolant Temperature Sensor Replacement.
-- --
Page 3of 4 Document ID: 1458885
Did you complete the replacement? Go to Step 13
12
Replace the ECM. Refer to EngineControl
Module Replacement.
Did you complete the replacement?
--
Go to Step 13
--
13
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 14
14
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
Page 4of 4 Document ID: 1458885