Diagnostic procedure

WARNING: This page is about a different car, the 2005 Mazda MX-5 Miata. However, it is still accessible from the selected car via links, so may be relevant.

DTC P0850 [BP, BP WITH TC] DIAGNOSTIC PROCEDURE

STEP	INSPECTION		ACTION
1	VERIFY FREEZE FRAME DATA HAS BEEN RECORDED Has FREEZE FRAME DATA been recorded?	Yes	Go to the next step.
1		No	Record FREEZE FRAME DATA on repair order, then go to the next step.
2	VERIFY RELATED REPAIR INFORMATION AVAILABILITY Check for related Service Bulletins and/or online repair information availably. Is any related repair information available?	Yes	Perform repair or diagnostic according to the available repair information If the vehicle is not repaired, go to the next step.
2		No	Go to the next step.
3	INSPECT NEUTRAL SWITCH SIGNAL CIRCUIT FOR SHORT TO GND Measure voltage between neutral switch connector terminal A and body GND. Is voltage 0 V ?	Yes	Repair or replace harness for short to GND, then go to Step 8.
3		No	Go to the next step.
4	INSPECT POOR CONNECTION OF NEUTRAL SWITCH CONNECTOR Turn the ignition switch off. Disconnect neutral switch connector. Check for poor connection (damaged, pulled-out terminals, corrosion, etc.). Is there any malfunction?	Yes	Repair or replace the terminal, then go to Step 8.
4		No	Go to the next step.
5	INSPECT NEUTRAL SWITCH GND CIRCUIT FOR OPEN CIRCUIT Check continuity between neutral switch terminal B (harness-side) and body GND. Is there continuity?	Yes	Go to the next step.
5		No	Repair or replace neutral switch connector GND circuit for open circuit, then go to Step 8.
6	INSPECT POOR CONNECTION OF PCM CONNECTOR Turn the ignition switch off. Disconnect PCM connector. Check poor connection (damaged, pulled-out terminals, corrosion, etc.). Is there any malfunction?	Yes	Repair terminal, then go to Step 8.
6		No	Go to the next step.
7	INSPECT NEUTRAL SWITCH SIGNAL CIRCUIT FOR OPEN CIRCUIT Disconnect neutral switch connector. Check continuity between neutral switch connector terminal A (harness-side) and PCM terminal 4H (harness-side). Is there continuity?	Yes	Go to the next step.
7		No	Repair or replace harness for open circuit, then go to Step 8.
8	INSPECT NEUTRAL SWITCH Preform neutral switch inspection. (See NEUTRAL SWITCH INSPECTION ) Is neutral switch okay?	Yes	Go to the next step.
8		No	Replace neutral switch, then go to the next step.
9	VERIFY TROUBLESHOOTING OF DTC P0850 COMPLETED Make sure to connect all disconnected connectors. Clear the DTC from the PCM memory using the WDS or equivalent. Drive vehicle 30 km/h {18.6 mph} or more. Shift up or down above 14 times while driving. Is same DTC present?	Yes	Replace PCM, then go to the next step.
9		No	Go to the next step.
10	VERIFY AFTER REPAIR PROCEDURE Perform the "AFTER REPAIR PROCEDURE ". (See AFTER REPAIR PROCEDURE ) Is any DTC present?	Yes	Go to the applicable DTC inspection. (See DTC TABLE )
10		No	Troubleshooting completed.