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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 P1602 [BP, BP WITH TC] DIAGNOSTIC PROCEDURE

STEP INSPECTION ACTION
1 VERIFY RELATED REPAIR INFORMATION AVAILABILITY 
  • Check for related Service Bulletins and/or online repair information availability.
  • Is any related repair information available?
 Yes Perform repair or diagnosis according to the available repair information.
  • If the vehicle is not repaired, go to the next step.
No Go to the next step.
2 DETERMINE IF NO DTC DETECTED OR SOME DTC DETECTED 
  • Clear the DTC from the PCM memory using the WDS or equivalent.
  • Turn ignition key to OFF and ON (Engine off).
  • Has DTC P1624 been detected?
 Yes Go to step 10.
No Go to the next step.
3 INSPECT IMMOBILIZER UNIT CONNECTOR FOR POOR CONNECTION 
  • Turn the ignition switch off.
  • Disconnect immobilizer unit connector.
  • Check for poor connection (damaged, pulled-out terminals, corrosion, etc.).
  • Is there any malfunction?
 Yes Repair or replace terminals, then go to Step 19.
No Go to the next step.
4 INSPECT GND CIRCUIT OF IMMOBILIZER UNIT FOR OPEN CIRCUIT 
  • Measure resistance between immobilizer unit terminal B (harness-side) and body GND.
  • Is there continuity?
 Yes Go to the next step.
No Repair or replace harness for open circuit, then go to Step 19.
5 INSPECT COIL TERMINAL 
  • Disconnect coil connector.
  • Check for bent terminals.
  • Is there any malfunction?
 Yes Repair or replace terminals, then go to Step 19.
No Go to the next step.
6 INSPECT COIL FOR SHORT CIRCUIT 
  • Check for continuity between coil terminal A (part-side) and body GND.
  • Is there continuity?
 Yes Replace coil, then go to Step 19.
No Go to the next step.
7 INSPECT COIL CIRCUIT FOR SHORT 
  • Connect coil connector.
  • Check for continuity between immobilizer unit terminal F (harness-side) and body GND.
  • Is there continuity?
 Yes Repair or replace harness for short circuit, then go to Step 19.
No Go to the next step.
8 INSPECT PCM CONNECTOR FOR POOR CONNECTION 
  • Disconnect PCM connector.
  • Check for poor connection (damaged, pulled-out terminals, corrosion, etc.).
  • Is there any malfunction?
 Yes Repair or replace harness, then go to Step 19.
No Go to the next step.
9 INSPECT COMMUNICATION LINE FOR OPEN CIRCUIT 
  • Measure continuity between immobilizer unit terminal A (harness-side) and PCM terminal 3S.
  • Is there continuity?
 Yes Go to Step 19.
No Repair or replace harness for open circuit, then go to Step 19.
10 CLASSIFY MALFUNCTION BY ANOTHER DETECTED DTCS 
  • Has DTC P1602 been detected?
 Yes Go to Step 14.
No Go to the next step.
11 INSPECT COIL CONNECTOR FOR POOR CONNECTION 
  • Disconnect coil connector.
  • Check for poor connection (damaged, pulled-out terminals, corrosion, etc.).
  • Is there any malfunction?
 Yes Repair or replace harness, then go to Step 19.
No Go to the next step.
12 INSPECT COIL FOR OPEN CIRCUIT 
  • Disconnect coil connector.
  • Measure resistance between coil terminals (part-side).
  • Is there continuity?
 Yes Go to the next step.
No Replace coil, then go to Step 19.
13 INSPECT COIL CIRCUIT FOR OPEN CIRCUIT 
  • Connect coil connector.
  • Measure the resistance between immobilizer connector terminals F and D (harness-side).
  • Is there continuity?
 Yes Go to Step 19.
No Repair or replace harness for open circuit, then go to Step 19.
14 DETERMINE IF MALFUNCTION BY ANOTHER DETECTED DTCS. 
  • Has immobilizer unit DTC 03 been detected?
 Yes Key has not transponder, replace with registered key. Go to Step 19.
No Go to the next step.
15 DETERMINE IF MALFUNCTION BY ANOTHER DETECTED DTCS. 
  • Has immobilizer unit DTC 01 been detected?
 Yes Key that using for ignition is not registered. Reprogram key or use another registered key, then go to the next step.
(See IMMOBILIZER SYSTEM REPROGRAM PROCEDURE )
No Go to the next step.
16 INSPECT POOR CONNECTION OF IMMOBILIZER UNIT CONNECTOR 
  • Turn the ignition switch off.
  • Disconnect immobilizer unit connector.
  • Check for poor connection (damaged, pulled-out terminals, corrosion, etc.).
  • Is there any malfunction?
 Yes Repair or replace harness, then go to the next step.
No Go to the next step.
17 INSPECT IMMOBILIZER UNIT POWER CIRCUIT FOR OPEN CIRCUIT 
  • Turn ignition key to ON (Engine off).
  • Measure voltage between immobilizer connector J (harness-side) and body GND.
  • Is voltage B+  ?
 Yes Go to the next step.
No Repair or replace harness for open circuit, then go to Step 19.
18 INSPECT COMMUNICATION LINE FOR SHORT HARNESS 
  • Measure resistance between immobilizer unit terminal A (harness-side) and body GND.
  • Is there continuity?
 Yes Repair or replace harness for short, then go to the next step.
No Go to the next step.
19 VERIFY TROUBLESHOOTING OF DTC P1602 COMPLETED 
  • Make sure to connect all disconnected connectors.
  • Clear the DTC from the PCM memory using the WDS or equivalent.
  • Turn ignition key to OFF, then start engine.
  • Is same DTC present?
 Yes Replace PCM, then go to the next step.
No Go to the next step.
20 VERIFY AFTER REPAIR PROCEDURE  Yes Go to the applicable DTC inspection. (See DTC TABLE )
No Troubleshooting completed.
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