6.6L LB7 or 8.1L L18 Engine Low Power, Will Not Go Over 2300 RPMs - kw C4500 C5500 GMT800 GMT560 diesel LB7 LLY L18 MAF no power pressure PTO shift speed switch automatic transmission
| Subject: | 6.6L LB7 or 8.1L L18 Engine Low Power, Will Not Go over 2300 RPMs. |
| Models: | . |
The following diagnosis might be helpful if the vehicle exhibits the symptom described in the PI.
Condition/Concern:
01-05 6.6L LB7 LLY or 8.1L L18 Engine low power, will not go over 2300 RPMs.
Recommendation/Instructions:
When diagnosing a low power complaint on a 6.6L or 8.1L engine, be sure to check the PTO switch. When the PTO switch is on, it will limit the engine speed between 2,000 and 2,300 RPM. If low power is verified and the PTO switch is on, lower than expected readings on the FRP Regulator Fuel Flow Command, Turbocharger Boost Pressure, and Mass Air Flow readings may be noticed. It may also cause changes in transmission operation such as long or delayed upshifts.
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Please follow this diagnosis 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. If these steps do not resolve the condition, please contact GM TAC for further diagnostic assistance.
Models:
(01 02 03 04 05 6.6 8.1 LB7 LLY L18 Chevrolet Silverado GMC Sierra C2 C3) and (01 02 03 04 05 6.6 8.1 LB7 LLY L18 Chevrolet Silverado GMC Sierra K2 K3) and (01 02 03 04 05 6.6 8.1 LB7 LLY L18 Chevrolet Kodiak GMC Topkick C4 C5 D4 D5 E4 E5)
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