my buddies 05 CCSB z71 is throwing these codes.


P0455 = Evaporative Emission control system detected (gross leak)

P0481 = cooling fan 2 circuit malfunction.

i cleared it with my EFI black box and as soon as we started the truck back up it came back.

how do i take care of these problems.

 

Here's the Bulletin and repair on the P0455

Subject: SES MIL on DTC P0442 and or P0455


Models: 2005 Chevrolet Silverado 3500 Chassis Cab

2005 GMC Sierra 3500 Chassis Cab




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The following diagnosis might be helpful if the vehicle exhibits the symptom(s) described in this PI.

Condition/Concern:
Some customers may comment that they receive a SES MIL relative to EVAP emission with a DTC P0442 and/or P0455 stored on Cab Chassis models. Root cause may be the fuel cap is ratcheting prior to being fully seated because the threads are not fully developed causing an interference. This is due to the upper fuel pipe assembly not being produced to specifications.

Recommendation/Instructions:
Dealers need to replace the upper fuel pipe sub-assembly (new P/N 15217502) and/or the gas cap to correct this situation.

Please follow this diagnostic or repair process thoroughly and complete each step. If the condition exhibited is resolved without completing every step, the remaining steps do not need to be performed.

 

Here's on the second one.....

DTC P0480 or P0481
Circuit Description
The powertrain control module (PCM) controls the low speed cooling fan operation by grounding the low speed fan relay control circuit with an internal solid state device called a driver. For high speed cooling fan operation, the PCM grounds the high speed and S/P relay control circuit at the same time the low speed control circuit is grounded. Battery positive voltage is supplied to the low speed, high speed, and S/P fan relays. When the PCM is commanding a fan relay ON, the voltage of the control circuit should be low, near 0 volts. When the PCM is commanding a fan relay OFF, the voltage potential of the control circuit should be high, near battery voltage.

The PCM monitors the relay control circuits for the following conditions:

• Short to ground

• Short to voltage

• An open circuit

If the PCM detects an improper voltage level on the low or high speed driver circuits, then code P0480 or P0481 will set and the effected driver will be disabled.

• Cooling fan relay 1 control circuit refers to the low speed cooling fan relay

• Cooling fan relay 2 control circuit refers to the high speed cooling fan relay

DTC Descriptors
This diagnostic procedure supports the following DTCs:

• DTC P0480 Cooling Fan Relay 1 Control Circuit

• DTC P0481 Cooling Fan Relay 2 Control Circuit

Conditions for Running the DTC
• The ignition voltage is between 8-18 volts.

• The engine speed is more than 40 RPM.

• The ECM driver transitions from ON to OFF or from OFF to ON.

Conditions for Setting the DTC
• P0481--The PCM detects an open circuit on the high speed cooling fan relay control circuit.

• P0480--The PCM detects an open on the low speed cooling fan relay control circuit.

• The above condition is present for one second.

Action Taken When the DTC Sets
• The PCM will illuminate the malfunction indicator lamp (MIL) during the second consecutive trip in which the diagnostic test has been run and failed.

• The PCM will store conditions which were present when the DTC set as Freeze Frame and Failure Records data.

Conditions for Clearing the MIL/DTC
• The PCM will turn OFF the MIL during the third consecutive trip in which the diagnostic has been run and passed.

• The History DTC will clear after 40 consecutive warm-up cycles have occurred without a malfunction.

• Use the scan tool Clear DTC Information function.

Diagnostic Aids
• If the condition is not present, refer to Testing for Intermittent Conditions and Poor Connections .

• Review the Freeze Frame/Failure Records vehicle mileage since the diagnostic test failed. This may help determine how often the condition that caused the DTC to be set occurs.

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

Listen for an audible click when the low speed fan relay operates. Command both the ON and OFF states. Repeat the commands as necessary.

Listen for an audible click when the S/P and high speed fan relays operate. Command both the ON and OFF states. Repeat the commands as necessary.