Note On Intermittents For Flow Chart 2

The PCM code snapshot provides valuable information in diagnosing an intermittent Code E91. If all digits of L.2.2 and L.2.3 are 1, check for an intermittent loss of ground to the park/neutral switch. If an intermittent Code E91 occurs when the transmission shift lever is moved, code is most likely caused by a misadjustment of the shift linkage or park/neutral switch, causing switch to end up in the range between gears.

If the code occurs and SERVICE ENGINE SOON light comes on while driving or when gear selector has not been moved, record L.2.2 and L.2.3 and compare values with chart. Check for intermittent open in circuit No. 773. Manipulate related wiring connectors while observing parameters P.2.2 and P.2.3 or "Scan" tester display. If an intermittent is induced, the digit corresponding to that circuit will change. If wiring or connectors are okay, substitute with a known good park/neutral switch and retest.

Fig 1: PCM Code E91, Schematic, Park/Neutral Switch Problem

Fig 2: PCM Code E91, Flow Chart, (1 of 2) Park/Neutral Switch Problem

Fig 3: PCM Code E91, Flow Chart, (2 Of 2) Park/Neutral Switch Problem