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Code 12 and code 21


foamf1

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I have a 97 tj 4.0L, I get a code 12 for interruption in power to the ecm. Jeep runs fine, after sitting over night the code goes away. Also get code 21 at the same time.
 

pagrey

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Most of the codes I have seen are like P0012 or P0021 which don't really match anything I could find. How are you getting your codes?
 
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foamf1

foamf1

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Most of the codes I have seen are like P0012 or P0021 which don't really match anything I could find. How are you getting your codes?
Turning the key on and off 3 times and counting the flashes of the check engine light, the codes also show up in the odometer area.
 

tworley

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The 97 codes are a bit odd. Code 12 means that the battery has been disconnected within the last 50 starts (or some number like that). Mine has always popped up even when the battery hasn't been disconnected. 21 is an o2 sensor (most likely upstream).
 

tworley

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FWIW....

The Codes - 1997 Models:


11 No crank reference signal detected during engine cranking. Intermittent loss of either camshaft or crankshaft position sensor. CKP sensor target windows have too much variation.

12 Direct battery input to PCM was disconnected within the last 50 Key-on cycles.

13 No difference recognized between the engine MAP reading and the barometric (atmosphere) pressure reading from start-up.

14 MAP sensor input above or below acceptable voltage. 5 volt output to MAP sensor open.

15 No vehicle speed sensor signal detected during road load conditions.

17 Engine did not reach operating temperature within acceptable limits. Engine does not reach 20º F. within 5 minutes with a vehicle speed signal.

21 Upstream oxygen sensor response slower than minimum required switching frequency. Upstream oxygen sensor heating element circuit malfunction. Downstream oxygen sensor heating element circuit malfunction. Downstream oxygen sensor input voltage maintained above the normal operating range. Oxygen sensor voltage too low, tested after cold start. (Upstream or Downstream) Left oxygen sensor input voltage maintained above the normal operating temperature.

22 Engine coolant temperature sensor above or below acceptable voltage.

23 Intake air temperature sensor input above or below acceptable voltage.

24 Throttle position sensor input above or below acceptable voltage. TPS signal does not correlate to MAP sensor.

25 A shorted or open condition detected in one or more of the idle air control motor circuits. Actual idle speed does not equal target idle speed.

27 Injector #3, and/or 4, and/or 5, and/or 6 output driver does not respond properly to the control signal.

31 An open or shorted condition detected in the A/C clutch relay circuit. Insufficient or excessive vapor flow detected during evaporative emission system operation.

33 An open or shorted condition detected in the duty cycle purge solenoid circuit.

34 An open or shorted condition detected in the Speed Control vacuum or vent solenoid circuits. Speed control switch input below the minimum acceptable voltage.

37 Relationship between engine speed and vehicle speed indicates no torque converter clutch engagement. An open or shorted condition detected in the torque converter part throttle unlock solenoid control circuit. Incorrect input state detected for the Park/Neutral switch. Auto only.

41 An open or shorted condition in the generator field control circuit.

42 An open or shorted condition detected in the auto shutdown relay circuit. An open condition detected in the ASD relay output circuit. An open or shorted condition detected in the fuel pump relay control circuit. An open circuit between PCM and fuel gauge sending unit. Circuit shorted to voltage between PCM and fuel gauge sending unit. No movement of fuel level sender detected.

43 Peak primary circuit current not achieved with maximum dwell time. Misfire detected in one or more cylinders 1 thru 6. (4 and 6 cyls.)

44 Battery temperature sensor in voltage above or below acceptable range.

46 Battery voltage sense input above target charging voltage during engine operation.

47 Battery voltage sense input below target charging during engine operation. Also, no significant change detected in battery voltage during active test of generator output circuit.

51 A lean air/fuel mixture has been indicated by an abnormally rich correction factor.

52 A rich air/fuel mixture has been indicated by an abnormally rich correction factor.

53 PCM Internal fault condition detected.

54 No camshaft signal detected during engine cranking.

55 Completion of fault code display on Check Engine lamp.

63 Unsuccessful attempt to write to an EEPROM location by the PCM.

64 Catalyst efficiency below required level. (Same as code 72)

65 Power steering high pressure seen at high speed. (2.5L only)

72 Catalyst efficiency below required level. (Same as code 64)

77 Malfunction detected with poser feed to speed control servo solenoids
 
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Wildman

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The 97 codes are a bit odd. Code 12 means that the battery has been disconnected within the last 50 starts (or some number like that). Mine has always popped up even when the battery hasn't been disconnected. 21 is an o2 sensor (most likely upstream).
Yes our 1997's are a finnicky bunch. Between the early & later wiring differences and then who knows what else they thought about throwing onto these rigs. Mine is a 01/96 build so one of the first off the assembly line. But there really isn't much left stock on mine so I guess it really doesn't matter.
 
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