Hello there is a service bulletin for the codes P0203 and p2149. It states that there could be a wire chafing problem for the fuel injector wiring harness rubbing through the alternator bracket. I would go over the harness and check the wires individually because there could be a break inside the wire coating.I'll give you the information for this issue.
Malfunction Indicator Lamp (MIL) Illuminated, Fuel Injector Driver Circuit DTCs and Cylinder Bank Shut Down DTCs, Reduced Engine Power (Repair Fuel Injector Control Module (FICM) Harness Chafed Wires) - (Aug 17, 2009)
Some customers may comment that the malfunction indicator lamp (MIL) is illuminated or intermittent and there is a significant reduction in engine power (limp home mode).
The scan tool may display one or more Injector Driver Circuit DTCs P0201, P0202, P0203, P0204, P0205, P0206, P0207 or P0208 and/or Cylinder Bank Shut Down DTCs P2146 or P2149 set as Current or in History.
This condition may be caused by the fuel injector control module (FICM) wiring harness protective conduit rubbing against the back of the alternator, the alternator bracket or the FICM harness retaining bracket. This may result in the conduit rubbing through, exposing the wires inside and chafing of the wire insulation then occurs.
Note: For Silverado and Sierra models only perform Step 5.
Important: DO NOT break off the tab on the electrical connectors.
Carefully bend up and backwards the FICM wiring harness electrical connectors (1) away from the FICM (4).
Note: Some of these chafes are very small, possibly the size of a pen tip, but could still cause injector circuit concerns.
If necessary, peel the tape from the area and look for ANY chafes into the wires.
Note: For Silverado and Sierra models only perform Step 11.
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