Engine RPM Limited to 4,000 RPM - Monitor TR Switch Input to TCM - keywords 4000 cut DTC early engine fuel high lean limit limiter low loss no off power range rev surge WOT

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

On rare occasions, the engine may not accelerate over 4,000 RPM while driving in any forward gear range. Upon inspection, there will be no DTCs stored and the O2 sensors may indicate that the exhaust is lean during this concern. This may be the result of an incorrect Transmission Range Switch Signal to the TCM, causing the ECM to enable fuel cut off mode around 4,000 RPM.

If the SI diagnostics do not isolate a cause for this concern, monitor the TR Switch Parameter in the Transmission Data List during the concern. If the TR Switch parameter is blank, incorrect, or reads invalid, compare the TR Switch A/B/C/P Parameter to the Transmission Range Switch Logic Table to determine which of the 4 TR Switch signals is incorrect. If an incorrect TR Switch signal is found, refer to the PNP Switch Schematic and inspect the related TR Switch Signal Circuit for an open, short to ground, or poor connection; repair the circuit as necessary. If there is no problem found with the circuit and an incorrect TR Switch signal is displayed, replace the TCM.

SI Document # 581838 - Transmission Range Switch Logic Table

SI Document # 1422126 - PNP Switch Schematic for 2005 Saturn Ion

SI Document # 1551962 - PNP Switch Schematic for 2006 Saturn Ion

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.