1st - P0420 bank 1 threshold below value. Now this is the front, because I have the rears turned off. Baut, it is also a new OEM sensor replaced in December. I have suspected the cats are bad (driver side one anyway) and haven't thrown the code foe 3 weeks. But, even before I turned the rears off I was throwing it. What is the temp procedure on testing a cat. Temp sme before and after, or temp higher before and cooler after means it's bad? I think it's the high/ low, but don't remember. I need to take it to the muffler shop and let them shoot some temps for me.

2nd - P0748 PC solenoid electric control. Never seen this one before.


Truck is running just fine as far as I can tell. I'm more concerned about the 2nd one.

 

The P0478 code is the Pressure control solenoid for the transmission line pressure. The manual says it can be set by a low voltage condition(bad wiring or low battery voltage below 8 volts). It also says that if the duty cycle of the valve is 0% or above 95% it can set the code.

Inspect circuit wiring for intermittent contacts. There is also a whole procedure listed in the manual for testing circuit resistances and such.

The first code is a low efficiency catalyst code. Sounds like your cat is toast, hollow it out and turn the code off.

 

greg do they do testing in tx for smog? if so then go ahead and get some new cats man. otherwise cut them bastards off. i just had mine cut off and i could tell a good difference. they weren't bad yet but on the verge of being bad. or yea do what xlr8nss said about hollowing them out. just make sure your muffler can handle all the extra air. my chokemaster is having it's insides blown out.

 

I don't like the sound of that trans code. I've got it set for 0% torque managment. I'm sure it's not in the wiring. Gotta be the line pressure. It shifts like a beast under normal throthle. Remeber when I said it was set for 9mph at 6%tps. Told you I didn't like that. Maybe I'll lower the line pressure a little and put that 1-2 back to 11mph at 6%tps.

As for the cats, yes we do have testing. I have had them off before when I made spools, and didn't notice ANYTHING power wise. What I did notice was the cheesy rasp it made. What I could do is get the Y redone and go back to a 3" or 3.5" single in dual out dumped. Pop in a 3.5" QTP cutout in behind the Y and a spool for a future cat and sensors after that. Should keep it legal for testing. They only test the PCM here for 96 and up, no dog sniffer. I'll keep the rears turned off anyway and probably won't even put them back in unless I have to get that cat put on.

 

the 0420 is the rear sensor on the passenger side (bank 1). Won't cause any running problems at all.

 

p0420 is not a code for the sensor. p0420 means the cat is not working properly. its almost always a bad cat. if your rear sensors are turned off you will not get this code. recheck your tune.

 

Damn, P0420 and P0430 codes are still on. I know how that happened now. When we did the tune, the first tune didn't load, so when we did it again, we must have forgot to go back and toggle the codes back off.

DOH!!! OK, that mystery is solved. Never thrown a front 02, but I'm still gonna have a temp profile shot on them jsut to verify. Lets keep discussing the other one.

 

you're right, but the code is thrown by the rear 02's. The rear 02's are input into the system simply to monitor the performance of the catalytic converter. That is why when you remove cats from the system you either need the pcm modified or instal 02 simms.

 

OK, time to bring this back up. I turned these codes off:
Driver side
P0137
P0138
P0140
P0141

Passenger side
P0157
P0158
P0160
P0161

I still get these two code at the same time. Weird. Why would I get a tranny code at the same time as a cat code, and why is this cat code still setting?

 

The Pressure Control Solenoid Valve (PC Sol. Valve) is an electronic device that regulates transmission line pressure based on the current flow through its coil winding. The magnetic field produced by the coil moves the solenoid's internal valve which varies pressure to the pressure regulator valve. The Powertrain Control Module (PCM) controls the PC Sol. Valve by applying a varying amount of amperage to the solenoid. The applied amperage can vary from 0.1 to 1.1 amps. Low amperage (0.1 amp) indicates high line pressure. High amperage (1.1 amps) indicates low line pressure. The duty cycle of the PC Sol. Valve is expressed as a percentage of energized ON time. Zero percent indicates zero ON time (non-energized) or no current flow. Approximately 60% at idle indicates maximum ON time (energized) or high current flow. The PCM determines the appropriate line pressure for a given load by comparing the Throttle Position (TP) voltage, the engine speed and other inputs.

When the PCM detects a continuous open or short to ground in the PC Sol. Valve circuit or the PC Sol. Valve, then DTC P0748 sets. DTC P0748 is a type D DTC.

Conditions for Setting the DTC
• The system voltage is 10-16 volts.

• The engine is running.

• The PC Sol. Valve Duty Cycle reaches its high limit (approximately 95%) or low limit (approximately 0%).

Action Taken When the DTC Sets
• The PCM does not illuminate the Malfunction Indicator Lamp (MIL).

• The PC Sol. Valve is OFF.

• The PCM freezes shift adapts from being updated.

• DTC P0748 stores in PCM history.

Conditions for Clearing the DTC
A scan tool can clear the DTC from the PCM history. The PCM clears the DTC from the PCM history if the vehicle completes 40 warm-up cycles without a failure reported.
The PCM cancels the DTC default actions when the fault no longer exists and the ignition is OFF long enough in order to power down the PCM.
Diagnostic Aids
• Inspect the wiring at the PCM, the transmission connector and all other circuit connecting points for the following conditions:

- A bent terminal

- A backed out terminal

- A damaged terminal

- Poor terminal tension

- A chafed wire

- A broken wire inside the insulation

- Moisture intrusion

- Corrosion

• When diagnosing for an intermittent short or open condition, massage the wiring harness while watching the test equipment for a change.

• DTC P0748 may set under low voltage conditions caused by high electrical system demands.

Test Description
The numbers below refer to the step numbers on the diagnostic table.

This step tests the ability of the PCM to command the PC Sol. Valve.

This step tests the PC Sol. Valve and Automatic Transmission Wiring Harness Assembly (A/T Wiring Harness Assembly) for incorrect resistance.

DTC P0748 Pressure Control Solenoid Valve Circuit -- Electrical (3.8L, VIN K) Step
Action
Value(s)
Yes
No

1
Was the Powertrain On-Board Diagnostic (OBD) System Check performed?
--
Go to Step 2
Go to Powertrain On Board Diagnostic (OBD) System Check

2
Install the Scan Tool .
With the engine OFF, turn the ignition switch to the RUN position.

Important
Before clearing the DTC(s), use the scan tool in order to record the Failure Records for reference. Using the Clear Info function will erase the stored Failure Records from the PCM.


Record the DTC Failure Records, then clear the DTC(s).
Start the engine.
Using the transmission output control function on the scan tool, apply 0.1 amp through 1.0 amp while observing PC Sol. Ref. Current and PC Sol. Actual Current.
Is the PC Sol. Actual Current always within the specified value of the PC Sol. Ref. Current?
0.16 amp
Go to Diagnostic Aids
Go to Step 3

3
Turn the ignition OFF.
Disconnect the transmission 20-way connector.
Install the J 39775 Jumper Harness on the transmission side of the 20-way connector.
Using the J 39200 Digital Multimeter (DMM) and J 35616-A Connector Test Adapter Kit, measure the resistance between terminal C and terminal D.
Is the resistance within the specified range?
3-7 ohms
Go to Step 8
Go to Step 4

4
Is the resistance greater than the specified value?
7 ohms
Go to Step 5
Go to Step 6

5
Inspect circuit 1228 (PPL) and circuit 1229 (LT BLU) of the A/T Wiring Harness Assembly for an open condition.

Refer to General Electrical Diagnosis Procedures .

Did you find an open condition?
--
Go to Step 18
Go to Step 10

6
Is the resistance less than the specified value?
3 ohms
Go to Step 7
--

7
Inspect circuit 1228 (PPL) and circuit 1229 (LT BLU) of the A/T Wiring Harness Assembly for a shorted together condition.

Refer to General Electrical Diagnosis Procedures .

Did you find a shorted condition?
--
Go to Step 18
Go to Step 10

8
Measure the resistance from terminal C to the transmission case.

Is the resistance greater than the specified value?
250K ohms
Go to Step 11
Go to Step 9

9
Inspect circuit 1228 (PPL) and circuit 1229 (LT BLU) of the A/T Wiring Harness Assembly for a short to ground condition.

Refer to General Electrical Diagnosis Procedures .

Did you find a short to ground condition?
--
Go to Step 18
Go to Step 10

10
Replace the PC Sol. Valve.

Refer to Control and Shift Solenoids Replacement .

Is the replacement complete?
--
Go to Step 20
--

11
Disconnect the J 39775 Jumper Harness from the transmission side of the 20-way connector.
Reconnect the transmission 20-way connector.
Disconnect the C2 (clear) PCM connector.
Using the J 39200 DMM and the J 35616-A Connector Test Adapter Kit, measure the resistance between terminal C2-45 and C2-46.
Is the resistance within the specified range?
3-7 ohms
Go to Step 16
Go to Step 12

12
Is the resistance greater than the specified value?
7 ohms
Go to Step 13
Go to Step 14

13
Inspect circuit 1228 (RED/BLK) and circuit 1229 (LT BLU/WHT) of the engine wiring harness for an open condition. Refer to General Electrical Diagnosis Procedures .
Repair the circuits if necessary. Refer to Wiring Repairs .
Did you find and correct an open condition?
--
Go to Step 20
--

14
Is the resistance less than the specified value?
3 ohms
Go to Step 15
--

15
Inspect circuit 1228 (RED/BLK) and circuit 1229 (LT BLU/WHT) of the engine wiring harness for a shorted together condition. Refer to General Electrical Diagnosis Procedures .
Repair the circuits if necessary. Refer to Wiring Repairs .
Did you find and correct a shorted condition?
--
Go to Step 20
--

16
Using the J 39200 DMM and the J 35616-A Connector Test Adapter Kit, measure the resistance from terminal C2-45 to ground.

Is the resistance less than the specified value?
9 ohms
Go to Step 17
Go to Step 19

17
Inspect circuit 1228 (RED/BLK) and circuit 1229 (LT BLU/WHT) of the engine wiring harness for a short to ground condition. Refer to General Electrical Diagnosis Procedures .
Repair the circuits if necessary. Refer to Wiring Repairs .
Did you find the short to ground condition?
--
Go to Step 20
--

18
Replace the A/T Wiring Harness Assembly.

Refer to Torque Converter Clutch Pulse Width Modulation (TCC PWM) Solenoid, TCC Solenoid, and Wiring Harness Replacement.

Is the replacement complete?
--
Go to Step 20
--

19
Replace the PCM.

Refer to PCM Replacement/Programming .

Is the replacement complete?
--
Go to Step 20
--

20
In order to verify your repair, perform the following procedure:

Select DTC.
Select Clear Info.
Start the engine and ensure that the following condition is met: The difference between the PC Sol. Valve actual return amperage and the desired amperage is less than 0.16 amp.
Select Specific DTC. Enter DTC P0748.
Has the test run and passed?
--
System OK
Go to Step 1