Why do I have a DTC PO204 never seen this before took off fuel rail the other day cleaned injectors and now have this code switched injector with another cylinder code stayed the same cylinder

Silverado 1500 or 2500 or 3500 or HD? no pickup told
not told the job you are doing>??
remove them all ,or scope them or just what, no job told
no end goal or task told. sorry can guess it.

like most V6/8 now , it is a sandwich.
the service manual covers all,l buy it rent it.?
toss dice and land on 1500
the rail on this engine, fuel rail like all , intake manifold injectors used;. all injector held down by both rails. left and right
now the steps to off them if is the job,
pull the isolator seen photo 1, far below.
1: pull left rail and right rail
Remove and discard the fuel injector retainer clips by installing EN-51097 injector retaining clip installer and spreading both sides of the clip evenly.
Always use NEW fuel injector collars supplied with injector when installing the new injector. If reinstalling the injector, it is not necessary to remove the collars unless the collars are being replaced.
Replace the injector seals as needed. Refer to Fuel Rail and Injectors Cleaning and Inspection.
Note
Inspect the injectors to be sure that they are clean and free of debris prior to installation. Do NOT lubricate the injector seals. Rebuild the fuel injectors whenever the injector has been removed from the fuel injector rail.


now I will past the other page rails off per the manual read to you.
just bank 1, i am to lazy to post both
step 1 rail off bank1.
Note
Inspect the injectors to be sure that they are clean and free of debris prior to installation. Do NOT lubricate the injector seals. Rebuild the fuel injectors whenever the injector has been removed from the fuel injector rail.

1. Remove the fuel pump insulator. Fuel Pump Insulator Replacement
2. Remove the fuel injector intermediate pipe position?1. Fuel Feed Intermediate Pipe Replacement - Position 1
3. Clean the cylinder head pocket around the injectors of any dirt or buildup.
4. Disconnect the electrical wiring harness connectors from the fuel rail.
5. the fuel rail fasteners are retained in the fuel rail by keepers and may be difficult to remove.Remove the fuel rail fasteners?(1) securing the injector rail?(2).
   Install two sets of EN-49248 remover?(3).
6. Install one remover in each of the fuel rail fastener bores.
7. Remove by turning each section of the EN-49248 remover an even amount to pull the fuel rail and injectors out evenly.
8. CAUTION
9. Remove the fuel rail assembly carefully in order to prevent damage to the injector electrical connector terminals and the injector spray tips. Support the fuel rail after the fuel rail is removed in order to avoid damaging the fuel rail components.
10. Cap the fittings and plug the holes when servicing the fuel system in order to prevent dirt and other contaminants from entering open pipes and passages.
11. 1. Simultaneously lift both ends of the fuel rail?(2) and remove the fuel rail assembly from the cylinder head.
12. Remove and DISCARD the fuel injector seals.
13. Some vehicles were not originally equipped with fuel injector dust seals. A NEW seal must be installed when the injectors are removed.
    Remove and DISCARD the fuel injector dust seal (1).
14. NOTE
    Note
    Whenever the fuel injectors are removed from the cylinder head or fuel rail, they will need to be rebuilt. Fuel Rail and Injectors Cleaning and Inspection
    If replacing the fuel injection fuel rail, remove the fuel injectors. Fuel Injector Replacement

Installation Procedure, skipped me. the service manual lists 4 tools
per

Special Tools

1. EN-49248 Injector Rail Assembly Remover
2. EN-51105-1 Injector Seal Installer and Sizer
3. EN-49245-3 Fuel Injection Seal Installer Sizer
4. EN-49245-4 Fuel Injection Seal Installer Sizer

this is first. pull the isolator.

this one step is the GET TO ANSWEREd
Injector work 10x more complex and special tools needed x4

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code p 0204 refers to injector 4--circuit malfunction===causes wiring--injector--ECM
by moving the injector if the problem moved it is in the injector ( (possible failing activation coil in the injector body)
if it stayed at the no 4 injector spot then it can be in the wiring , connections or a problem ECM

so missfire detected and cylinder 3 missfire detected.
check to see injector pulse with "noide light" if ok injector is problem
remove fuel rail and injectors look into top of injector for blockage in screen filter in injector if blocked clean out or injector carby places can remove this screen replace it and test injectors and clean or just buy new injectors. make sure to clean out fuel rail and change fuel filter also.
if noide light flashes irratic or not at all wiring issue, check for power on one wire with ignition on 12v other is earthed by ecu when opened to inject fuel. other thing that can cause problem on cylinder is tappet clearance "shims" too tight, could do compression test to see if compression is low on cylinder or a cylinder leakage test to see if valves are leaking. broken valve spring. valves do not hit piston on these engines even if cam belt breaks, they are a "free wheeling" engine

After a fill up, the fumes in the gas tank are very concentrated. If problem with evap system, it could cause problems after a fill-up. Just a thought.

Are you sure about your reading, Code 19 isn't listed.

DTC OBD I Code 34
Description: Speed control solenoid(s) circuit is open or shorted
Notes: For vehicles equipped with speed control

Possible Causes
- Bad connection or wiring - Check the wiring and connections between the logic module and the solenoid. Clean and regrease any corroded connectors with dielectric grease and repair any shorts.
- Bad solenoid(s) - The speed control is located near the battery and will have to be disassembled.


DTC OBD I Code 27
Description: Injector driver circuit 2 open or shorted

Possible Causes
- Bad connection or wiring - Check the wiring and connections to injectors 3 and 4 in the injector harness (above the fuel rail) and between the harness and the power module (or SMEC) and the injector contol lines between the logic module and power module. Clean and regrease any corroded connectors with dielectric grease and repair any shorts.
- Injector driver transistor failure - Check the injector signals coming from the power module (or SMEC). They should rise to about 12V when the injector is off and drop close to 0V when the injector is on. If they are out of spec, you may need to replace the power module.


DTC OBD I Code 55
Description: End of message

Possible Causes
No further fault codes are stored. If this is the only code received, then there are no codes stored in memory. This code will always be given, even if nothing is wrong. If you do not get this code, then you may not be retreiving the codes properly, or the power loss light may be burnt out. The light should come on for 1 second when the ignition is initally turned on as a bulb test.


I hope this helps; remember to rating this and just keep in mind that your feedback is important and I'll appreciate your time and consideration if you leave some testimonial comment.

Have a nice day and thanks for using FixYa.
Jose.

All fault codes can be checked out at http://www.bluejag.co.uk but here are the results for some of yours. You can ignor P1111. Looks like a faulty plug or coil pack cylinder 2

Fault Code:- P1314 Indicates a Power-train fault


The fault is generally due to a problem in the Ignition or Misfire area


Fault Description: Misfire rate catalyst damage -bank 2 NOTE: This DTC will flag only when accompanied by an individual cylinder misfire DTC: P0300 - P0306

Action of ECM:- ECM Default:- Maximum engine speed reduced


After clearing the DTC, complete the Misfire monitor drive cycle
Check for a reoccurrence of fault DTC.

Possible Fault:- Cylinder compression low Worn camshaft / broken valve spring(s) Fuel delivery pressure (low / high) Fuel injector(s) restricted / leaking Fuel injector(s) continuously open Fuel contamination Fuel injector circuit fault(s) (Injector DTCs also flagged) Spark plug failure / fouled / incorrect gap ECM to ignition coil primary circuit fault (Cylinder misfire detected DTC also flagged) Ignition coil failure
Fault Code:- P1316 Indicates a Power-train fault


The fault is generally due to a problem in the Ignition or Misfire area


Fault Description: Misfire excess emission NOTE: This DTC will flag only when accompanied by an individual cylinder misfire DTC: P0300 - P0306

Action of ECM:- none


After clearing the DTC, complete the Misfire monitor drive cycle
Check for a reoccurrence of fault DTC.

Possible Fault:- Cylinder compression low Worn camshaft / broken valve spring(s) Fuel delivery pressure (low / high) Fuel injector(s) restricted / leaking Fuel injector(s) continuously open Fuel contamination Fuel injector circuit fault(s) (Injector DTCs also flagged) Spark plug failure / fouled / incorrect gap ECM to ignition coil primary circuit fault (Cylinder misfire detected DTC also flagged) Ignition coil failure

Fault Code:-
P0302 Indicates a Power-train fault


The fault is generally due to a problem in the Ignition or Misfire area


Fault Description: Misfire detected ?€" cylinder 2

Action of ECM:- none


After clearing the DTC, complete the Misfire monitor drive cycle
Check for a reoccurrence of fault DTC.

Possible Fault:- Refer to P0300 Possible Causes

P0087- low pressure fuel system. Fuel pressur valve stock open, Fuel volume control valve stuck close, Leaking fuel injector,P0088- fuel pressure contorl valve stuck close, Fuel rail pressure sensor P2291-all @ at the above, means to say poor fuel quality

Removal & Installation


Exploded view of the fuel rail and injector mounting


Take care when servicing the fuel rail assembly to prevent dirt or contaminants from entering the fuel system. ALL openings in the fuel lines and passages should be capped or plugged while disconnected.

1. Before disassembly, clean the fuel rail assembly with a spray type cleaner such as AC Delco® X-30A, or equivalent. After removal, DO NOT immerse the fuel rail in liquid solvent.
   
2. Properly relieve the fuel system pressure and disconnect the negative battery cable.
   
3. Remove the air intake duct, as necessary for access.
   
4. Tag and disengage the fuel injector electrical connectors.
   
5. Disengage the fuel pressure regulator vacuum line, then tag and disengage all other necessary vacuum hoses.
   
6. Loosen and remove the fuel rail retaining bolts.
   
7. If necessary to remove the fuel rail assembly completely from the engine compartment, or to prevent stressing and damaging the fuel lines, disconnect the fuel lines from the rail assembly.
   
8. Carefully lift the fuel rail assembly and fuel injectors from the intake.
   
9. Carefully release and separate the fuel injectors from the rail assembly.
   
10. Remove and discard ALL old O-rings from the fuel injectors and, if disconnected, the fuel lines.
    

To install:

1. Lightly coat the new O-rings with clean engine oil, then position them to the injectors and, if applicable, fuel fittings.
   
2. Install the injectors to the fuel rail assembly.
   
3. Carefully install the fuel rail and injectors to the intake manifold. Make sure the injectors are properly seated in their bores, but DO NOT force them into position.
   
4. Install and tighten the rail retaining bolts to 62 inch lbs. (7 Nm).
   
5. If removed, connect the fuel lines to the rail assembly and secure the fittings.
   
6. Engage the fuel pressure regulator and any other vacuum lines, as noted during removal.
   
7. Engage the injector electrical connectors.
   
8. Connect the negative battery cable and cycle the ignition switch (without attempting to start the engine) in order to pressurize the fuel system, then check for leaks.
   
9. Install the air intake duct.
   

Have you checked that engine oil level is okay, if so check that oil pressure switch is good. The switch is usually bypassed to start the engine, but it won't run with no oil pressure indicated...hope this helps