Error codes after installing magnaflow cats

[PzYkED]

Sure could use some input here. Today I got my 04 H2 with 77k km on it back from a local car guy/welder that welded on some magnaflow cats to my original exhaust system. Turned out that both original cats was completely empty (no wonder i didnt pass the emissons test).

I have the diablosport trinity and ran the diagnostic tool after the new cats was installed, i got the codes P0135 and P0155. These codes never appeared before the change of cats. Erased the error codes, checked the connectors and drove around a bit. But the error codes pops back up.

Isnt it highly unlikely that both these sensors would go bad at the same time?
I didnt think that welding on new cats would destroy the sensors, but it sure seems like a possibility now.

Any help much appreciated

[HUMTECH]

check the O2A fuse in the underhood fuse block

[PzYkED]

Thanks for the tip Humtech

Checked both o2a and b. They looked fine. Also double checked the connectors and cables from each sensor.

Do you think that the welding process has fried the o2 sensors since they were left on when the cats were welded on? or are there other things i could check before ordering new sensors.

Thanks again

[HUMTECH]

DTC P0135 or P0155Step
Action
Value(s)
Yes
No
Schematic Reference: Engine Controls Schematics
Connector End View Reference: Engine Controls Component Views or Powertrain Control Module Connector End Views
1
Did you perform the Diagnostic System Check?Engine Controls?
?
Go to <a id="s02_rev">Step 2
Go to Diagnostic System Check - Engine Controls
2
Important: Whenever the HO2S heaters are commanded ON with a scan tool, they will continue to be pulsed ON once per second until the ignition is turned OFF for 30 seconds.

1. Turn ON the ignition, with the engine OFF.
2. Command the HO2S heaters ON with a scan tool.
3. Wait 15 seconds to allow the HO2S heater current to stabilize.
4. Observe the affected HO2S heater current parameter with a scan tool.

Is the HO2S heater current parameter within the specified range?
0.25?3.125 A
Go to <a id="s03_rev">Step 3
Go to <a id="s06_rev">Step 6
3
Observe the Freeze Frame/Failure Records for this DTC.
Did the DTC fail with an engine run time of less that 10 seconds?
?
Go to <a id="s04_rev">Step 4
Go to <a id="s05_rev">Step 5
4

1. Operate the vehicle within the Conditions for Running the Heater Resistance Test.
2. Start the engine.

Did the DTC fail this ignition?
?
Go to <a id="s06_rev">Step 6
Go to Intermittent Conditions
5

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 Heater Current Test. 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 <a id="s06_rev">Step 6
Go to Intermittent Conditions
6
Inspect the O2A fuse.
Is the O2A fuse open?
?
Go to <a id="s07_rev">Step 7
Go to <a id="s08_rev">Step 8
7
Test the ignition 1 voltage circuit for a short to ground. Refer to Circuit Testing and Wiring Repairs in Wiring Systems.
Did you find and correct the condition?
?
Go to <a id="s22_rev">Step 22
Go to <a id="s10_rev">Step 10
8

1. Disconnect the affected HO2S.
2. Turn ON the ignition, with the engine OFF.
3. Probe the ignition 1 voltage circuit of the HO2S harness connector on the engine harness side with a test lamp that is connected to a good ground. Refer to Probing Electrical Connectors in Wiring Systems.

Does the test lamp illuminate?
?
Go to <a id="s09_rev">Step 9
Go to <a id="s19_rev">Step 19
<a id="td09_rev"><a href="http://gsi.xw.gm.com/newsi/showDoc.do?docSyskey=1250611&cellId=66527&pubObjSy skey=3144813&from=sm&pubCellSyskey=642081&delivery EffectiveDate=May+1%2C+2013#td09">9
Important: The test lamp may blink prior to commanding the heaters ON. This is because the heaters were commanded ON in a previous step. To command the heaters OFF, turn OFF the ignition for 30 seconds.

1. Connect a test lamp between the ignition 1 voltage circuit of the HO2S harness connector on the engine harness side and the HO2S heater low control circuit of the HO2S harness connector on the engine harness side.
2. Command the HO2S heaters ON with a scan tool.

Does the test lamp blink once per second?
?
Go to <a id="s11_rev">Step 11
Go to <a id="s12_rev">Step 12
10
Important: Perform the following test on all HO2S' which are supplied voltage by the suspect circuit.

Test the ignition 1 voltage circuit on the sensor side of the HO2S connector for a short to ground. Refer to Circuit Testing in Wiring Systems.
Is any sensor shorted to ground?
?
Go to <a id="s20_rev">Step 20
Go to Intermittent Conditions
11
Measure the resistance of the following circuits with a DMM:

• HO2S heater low control circuit
• Ignition 1 voltage circuit

Refer to Circuit Testing in Wiring Systems.
Is the resistance of either circuit more than the specified value?
3 Ω
Go to <a id="s18_rev">Step 18
Go to <a id="s16_rev">Step 16
12
Is the test lamp on steady?
?
Go to <a id="s13_rev">Step 13
Go to <a id="s14_rev">Step 14

[HUMTECH]

13
Test the HO2S heater low control circuit for a short to ground. Refer to Circuit Testing and Wiring Repairs in Wiring Systems.
Did you find and correct the condition?
?
Go to <a id="s22_rev">Step 22
Go to <a id="s17_rev">Step 17
14
Test the HO2S heater low control circuit for a short to voltage. Refer to Circuit Testing and Wiring Repairs in Wiring Systems.
Did you find and correct the condition?
?
Go to <a id="s22_rev">Step 22
Go to <a id="s15_rev">Step 15
15
Test the HO2S heater low control circuit for an open or high resistance. Refer to Circuit Testing and Wiring Repairs in Wiring Systems.
Did you find and correct the condition?
?
Go to <a id="s22_rev">Step 22
Go to <a id="s17_rev">Step 17
16
Test for shorted terminals and for poor connections at the HO2S. Refer to Testing for Intermittent Conditions and Poor Connections and Connector Repairs in Wiring Systems.
Did you find and correct the condition?
?
Go to <a id="s22_rev">Step 22
Go to <a id="s20_rev">Step 20
17
Test for shorted terminals and for poor connections at the PCM. Refer to Testing for Intermittent Conditions and Poor Connections and Connector Repairs in Wiring Systems.
Did you find and correct the condition?
?
Go to <a id="s22_rev">Step 22
Go to <a id="s21_rev">Step 21
18
Repair the circuit with high resistance. Refer to Wiring Repairs in Wiring Systems.
Did you complete the repair?
?
Go to <a id="s22_rev">Step 22
?
19
Repair the open or high resistance in the ignition 1 voltage circuit. Refer to Wiring Repairs in Wiring Systems.
Did you complete the repair?
?
Go to <a id="s22_rev">Step 22
?
20
Replace the affected HO2S. Refer to Heated Oxygen Sensor Replacement - Bank 1 Sensor 1 or Heated Oxygen Sensor Replacement - Bank 2 Sensor 1.
Did you complete the replacement?
?
Go to <a id="s22_rev">Step 22
?
21
Replace the PCM. Refer to Powertrain Control Module Replacement.
Did you complete the replacement?
?
Go to <a id="s22_rev">Step 22
?
22
Were you sent to this diagnostic from DTC P0134 or P0154?
?
Go to Step 17 in DTC P0134 or P0154
Go to <a id="s23_rev">Step 23
23

1. Replace the O2A fuse if necessary.
2. Clear the DTCs with a scan tool.
3. Turn OFF the ignition for 30 seconds.
4. Start the engine.
5. 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 <a id="s02_rev">Step 2
Go to <a id="s24_rev">Step 24
24
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

[PzYkED]

Got the new o2 sensors last week, put them in and the error codes is a thing of the past

So I would recommend everybody to remove the sensors before welding on new cats in the future, since its now 100% sure that the welding fekked up the sensors.