Code B127
(Page 1 of 2) PRNDL CIRCUIT
Circuit Description:
The PRNDL (gear selector) switch is mounted on the transaxle assembly. It is a multi-signal switch sending information relative to gear selector position to the BCM and ECM. The PRNDL position sensor portion of the switch operates as a potentiometer. The BCM provides PRNDL reference voltage (B+) to the sensor on CKT 343 and a ground on CKT 736. The wiper sends par selector position to the BCM as a voltage signal on CKT 356. To reduce variation from system voltage fluctuation, the signal is calculated as a % of reference voltage. The switch also provides P/N input to the ECM, reverse input to the BCM and back-up lamps, and acts as a P/N start switch. Code B 127 will set if signal % is above or below normal range, or if gear position inputs conflict. Code B 127 causes include:
^ CKT's 343, 350, 356, 434 or 736 are open or grounded.
^ Faulty terminal contacts on any of the above circuits.
^ Faulty switch adjustment or switch.
^ Sensor signal % does not indicate "R" when reverse input is high.
^ Sensor signal % does not indicate "P/N" when crank input is high.
^ Sensor signal % does not agree with "P/N" input to ECM on CKT 434.
Test Description: The following numbered steps correspond with the step numbers on the diagnostic chart.
CHART B127PRNDL CIRCUIT:
1. Checks BD41 value to determine if PRNDL is within range or outside the range of normal values which are shown on the code chart.
2. With a low BD41 value, fault could be a misadjusted PRNDL switch, as well as an open or ground in CKT 343 or 356.
3. A high value indicates an open in ground side of the PRNDL circuit. The open could be in the switch or in CKT 736 up to its splice with the other sensors.
Notes on Intermittents If the gear selector is stopped between gears the code could set. Check linkage for binding and adjustment. Also manipulate related wiring. Check for proper terminal contact at BCM IC13 and 2B3 if equipped with illuminated PRNDL in IPC. If good contacts and B127 continues to set, replace BCM.
CODE B127
(Page 2 of 2) PRNDL CIRCUIT
Circuit Description:
The PRNDL (gear selector) switch is mounted on the transaxle assembly. It is a multi-signal switch sending information relative to gear selector position to the BCM and ECM. The PRNDL position sensor portion of the switch operates as a potentiometer. The BCM provides PRNDL reference voltage (B+) to the sensor on CKT 343 and a ground on CKT 736. The wiper sends par selector position to the BCM as a voltage signal on CKT 356. To reduce variation from system voltage fluctuation, the signal is calculated as a % of reference voltage. The switch also provides P/N input to the ECM, reverse input to the BCM and back-up lamps, and acts as a P/N start switch. Code B 127 will set if signal % is above or below normal range, or if gear position inputs conflict. Code B127 causes include:
^ CKT's 343, 350, 356, 434 or 736 are open or grounded.
^ Faulty terminal contacts on any of the above circuits.
^ Faulty switch adjustment or switch.
^ Sensor signal % does not indicate "R" when reverse input is high.
^ Sensor signal % does not indicate "P/N" when crank input is high.
^ Sensor signal % does not agree with "P/N" input to ECM on CKT 434.
Test Description: The following numbered steps correspond with the step numbers on the diagnostic chart.
CHART B127PRNDL CIRCUIT:
1. This step checks the PRNDL "P/N" input to the ECM in each gear range.
2. This step checks the PRNDL reverse input to the BCM in each gear range.
3. This step checks the PRNDL "P/N" crank input to the BCM.
Notes on Intermittents If the gear selector is stopped between gears the code could set. Check linkage for binding and adjustment. Also manipulate related wiring. Check for proper terminal contact at BCM 1C13 and 2B3 if equipped with illuminated PRNDL in IPC. If good contacts, and B127 continues to set replace BCM. If code sets only with lights "ON," check for voltage back feed on Backup lights circuit to BCM terminal 1C13. Refer to section "8A" for circuit details.