Reading Computer Codes
On 1991 to1997 models ( 1984 to 1986 V6 models as well as 1998 to 2002 follow ) you have a way of reading for fault codes which can be accessed without any scanners like other models by reading how the check engine light flashes. Start by turning the ignition key to the last stop before it starts, on and off three times within 5 seconds ending in the on position on the third time, ( i.e. on, off, on, off then on and hold ). The check engine light will start to flash quickly with a small pause in between then a medium pause to indicate the next number in the to digit number and then a long pause before the next set of flashing for the next code. If all is well you will get a code 55 which would read like this: 5 fast flashes, medium pause then a further 5 flashes. This is how all codes end with is this 55 code if you have air conditioning or with a code 33 without and any other codes would have been before it separated by a long pause. The codes will remain after this test so you can cycle through it as many times as it takes to read them. After a problem has gone the code will be removed after 50 on off key cycles or if the battery left disconnected over night which will cause a code 12 though.
Code Description Most likely reason
11 No crank signal to computer. Fault in wiring between crankshaft position sensor (CPS) and ECM ( PCM or computer ) or faulty CPS.
12 Battery disconnected. Battery or power to the ECM disconnected in the last 50 key cycles.
13 MAP Sensor. No change in Manifold Absolute Pressure (MAP) between engine off and on. Check circuit and MAP sensor.
14 MAP Sensor. MAP sensor voltage too high or low. Check circuit and sensor.
15 Speed sensor or circuit. No signal detected from speed sensor. Check circuit and sensor.
17 Engine running too cold. Wrong or faulty thermostat. Check also sensor and circuit for fault.
21 Oxygen sensor or circuit. O2 sensor or wiring faulty.
22 Coolant sensor or circuit. Check temp sensor and wiring.
23 Intake air temp or circuit. Check air temp sensor and wiring.
24 Throttle Position Sensor (TPS) Check TPS sensor and wiring.
25 Idle Air Control circuit (IAC) Check IAC sensor and wiring.
26 Injector circuit resistance. Peak injector current has not been reached or injector circuits have resistance
27 Fuel injector control circuit. Will need specialist diagnostics.
31 Evaporative control circuit. Fault in fuel evaporative control circuit or hoses.
33 Air conditioning clutch relay. Wiring to A/C clutch fault.
34 Cruise control circuit. Fault in circuit.
35 Cooling fan relay. Check relay and circuit.
36 Air switch solenoid circuit. Air switch solenoid circuit (non-turbo) or the waste gate solenoid on turbocharged models
37 Torque converter clutch. Needs specialist or dealer diagnostics.
41 Alternator field switch. Switch not operating correctly and check charging system.
42 Automatic shutdown relay. Check relay and circuit. Needs specialist or dealer diagnostics.
43 Misfire. Misfire in one or more cylinders.
44 Battery temperature sensor. Needs specialist or dealer diagnostics.
46 Battery over voltage. Check charging system.
47 Battery under voltage. Check charging system.
51 O2 detects lean mixture. Check sensor and circuit and for vacuum leaks.
52 O2 detects rich mixture. Check fuel injection system and sensor.
53 Powertrain Control Module. PCM (ECM) fault. Needs specialist or dealer diagnostics.
54 Distributor sync pickup. Change sync sensor in distributor.
55 End of code. Trouble codes finished or none recorded.
61 BARO solenoid BARO solenoid failure
62 Emissions reminder. Emissions maintenance reminder. Needs specialist or dealer diagnostics.
63 Controller failure. EEPROM write denied. Needs specialist or dealer diagnostics.
64 Flexible fuel sensor. Flexible fuel (methanol) sensor indicates concentration sensor input more/less than acceptable voltage
65 Manifold tune value. Manifold tune valve solenoid circuit open or shorted
66 TCM to PCM failure. No message from the Transmission Control Module (TCM) to the Powertrain Control Module (PCM)
72 Catalytic converter circuit. Needs specialist or dealer diagnostics.
76 Fuel pump bypass relay circuit. Needs specialist or dealer diagnostics.
77 Cruise control system. Check power to cruise control solenoids.
On 1984 to 1986 V6 only models the codes can also be read. First locate the diagnostics connector which is on the left fender well and is divided into two sections with six in the lower section ( 3 rows of 2 ) and fifteen in the upper section ( 3 rows of 5 ). In the upper section you have to run a wire between terminal six ( first row 4 down from the top ) and terminal 7 ( third row 3 down from the top ). Then turn the key into the on position making sure not to start it while these terminals are connected at any time. It should flash the code 12 ( 1 flash, pause, 2 flashes ) three times in a row and will repeat this sequence until disconnected if no other codes are recorded. If there are any faults stored then they will follow afterwards repeating themselves three times before moving on to the next code. To clear to codes remove negative cable for 10 seconds or longer.
Code Description Most likely reason
12 Terminals 6 and 7 connected. If appears when terminals not connected and engine running, no signal between distributor and computer.
13 Oxygen sensor circuit. Check TPS adjustment. Check O2 wiring and sensor.
14 Coolant sensor circuit. Overheating or fault in wiring or coolant sensor.
15 Coolant sensor circuit. Low temperature or fault in wiring or coolant sensor.
21 TPS circuit. Signal voltage high. Check TPS and adjustment. Also wiring at both computer and TPS ends.
23 Mixture control (M/C). Check wiring at M/C solenoid and computer. Clear code and re-check after driving.
34 MAP sensor. Check wiring and hose in case of leak. Otherwise replace.
41 No distributor signal. Check distributor wiring and pick-up coil connections.
42 EST or bypass problem. Check wire to terminal 12 on ECM or faulty HEI module can cause same code.
44 Lean exhaust. Check for sticking M/C solenoid also terminals 9 and 14 at ECM. Vacuum leakage or faulty O2 sensor.
44-45 O2 sensor or circuit. O2 circuit wiring or sensor faulty.
45 Rich exhaust. Check for sticking M/C solenoid and wiring plus charcoal canister for fuel. O2 sensor faulty.
51 PROM fault. Needs specialist or dealer diagnostics.
54 M/C solenoid Check wiring at M/C and ECM. Faulty M/C.
55 Reference voltage. Check short to ground on ECM terminal 21 wire. O2 sensor or ECM faulty.
For the 1998 to 2002 models you can access the trouble codes as follows. Insert the key but do not turn. Fully depress the trip reset button and hold down. Next turn the key to the on position three times and then leave in the on position. Release trip reset button and the gauges will flicker and the odometer will count down and then show the trouble codes. I have been told that some 1997's you don't need to use the trip button but cycle the key off and on 5 times! Just try one way or the other if it does not work for you. There was also someone that told me it would not work unless they had a warm engine and there are a few theories that it will not work after '97 as Jeep did not like people finding the faults and having them repaired under warranty. I have done some searching for as many technics as possible hoping that one will work for the post '97 models ( '97 does still work as does early '98 as above ). These are from other Chrysler vehicles.
• Simultaneously press the trip reset and trip/odometer switches; while holding them, turn the ignition to RUN (not start), and wait about five seconds. This sends the car through a short self-test sequence that lights all segments of the odometer and shift selector read-out (where applicable). It will then display the stored error codes.
• Normally, to get codes, you put the key on OFF and then rapidly do OFF-ON-OFF-ON-OFF-ON. Mark Warrington was able to use the blinking check engine light and the odometer readout after doing five on/ five off ignition sequences, and if the check engine light was on, on his 4-liter 1996 Grand Cherokee.
• A loose gas cap may light up the Check Engine light! (Thanks, Lyn Clark)
• James Hale's 2000 Grand Voyager has the following sequence.
1. Press the trip and trip-reset buttons that are located next to the digital odometer.
2. Turn the ignition key to "Run" or "On" and not "Start".
3. Count five seconds or better yet, if you didn't buckle-up count five chimes.
4. Release both buttons at the same time. Then the word "Codes" shows up in the odometer, and a self-test seems to take place; I always get "999" which I assume is the end-of-codes number. After that, a series of tests show up: "Code 1", "Code 2" and "Code 3" which test the gauges, lights and LEDs in the instrument panel, including the trip-computer/compass.
• On Elko Tchernev's 1998 Stratus, where there is only one combined trip/odometer and reset switch, waiting for 5 seconds will just reset the trip odometer. To get codes, press the switch, turn the ignition to ON, and release the switch as soon as the odometer displays "Check 1". This causes the computer to go through several check sequences (5, IIRC), for all lamps, LED segments and gauges, indicated by "Check 2" etc. and terminated by "End". BUT Al Ward wrote that this only checks the sensors feeding the instrument panel.
11 No camshaft reference during cranking signal detected during engine cranking.
12 Battery power to PCM was disconnected.
13 No variation in MAP from start to run sensor is detected. No difference recognized between engine MAP reading and barometric pressure reading at start- up.
14 MAP sensor input below or above acceptable voltage.
15 No vehicle speed signal. No vehicle distance (speed) sensor signal detected during road load conditions or shaft speed less than 60 rpm when speed above 15 mph.
17 Engine is cold too long. Engine coolant temperature remains below normal operating temperatures during vehicle travel (thermostat).
21 O2 sensor voltage not detected from the oxygen sensor input. Or 02 sensor input voltage maintained above or below normal operating range.
22 Coolant sensor voltage. Sensor input above or below acceptable voltage.
23 Charge air temp. sensor. Sensor input above or below acceptable voltage.
24 TPS voltage sensor input above or below the minimum acceptable voltage. Or TPS signal does not correlate to MAP sensor.
25 AIS motor circuits. An open or shorted condition detected in one or more of the IAC control circuits. Or target idle speed not met.
26 Peak injector current has not been reached or injector circuits have resistance
27 Injector # X control circuit Injector output driver does not respond properly to the control signal.
31 An open or shorted condition in Purge Solenoid circuit. Incorrect vapour flow detected. Possible leak or blocked between solenoid and fuel tank.
33 A/C clutch relay circuit An open or shorted condition detected in the A/C clutch relay circuit.
34 S/C solenoid circuits An open or shorted condition detected in the speed control vacuum or vent solenoid circuits. Voltage too high or low.
35 Radiator Fan Relay in open or shorted condition detected in the radiator fan relay circuit. ( 2.5L only ).
36 Air switch solenoid circuit (non-turbo) or the wastegate solenoid on turbocharged models
37 No speed difference detected at 3 to 4 shift or no lockup in torque converter. Problem with trans solenoid with wrong pressure or voltage. Speed to trans ratio below minium required. Park/Neutral switch stuck.
41 Alternator field circuit in open or shorted condition detected in the alternator field control circuit.
42 ASD ( auto shut down ) or fuel pump relay control circuit in open or shorted condition detected. Or no voltage sensed at controllers. No fuel sensor signal detected or changed over time at PCM.
43 Cylinder misfire detected.
44 Battery temperature voltage out of range ( too high or low ).
45 Trans temperature/ Governor pressure voltage out of range. Less than 1.55 or above 3.73volts for temperature and less than .1 or above 4.89 volts. Trans temp. to high or low. OD switch input too low for more than 5 mins.
46 Charging system voltage high. Battery voltage sense input above target charging voltage during engine operation.
47 Charging system voltage low. Battery voltage sense input below target charging voltage during engine operation.
51 O2 signal below centre. Oxygen sensor signal indicates lean fuel/air ratio condition during engine operation.
52 O2 signal above centre. Oxygen sensor signal indicates rich fuel/air ratio condition during engine operation or Adaptive memory at lean limit.
53 Internal Controller failure in PCM. Internal Controller fault condition detected.
54 No Sync signal. No camshaft position signal detected during engine cranking.
61 BARO solenoid failure
62 Controller failure. EMR miles not stored.
63 Failure to write to EEPROM location by PCM.
64 Flexible fuel (methanol) sensor indicates concentration sensor input more/less than acceptable voltage.
65 Manifold tune valve solenoid circuit open or shorted
66 No message from the Transmission Control Module (TCM) to the Powertrain Control Module (PCM)
72 Catalyst efficiency below required level.
76 Fuel pump resistor Open or shorted condition by-pass relay circuit detected in fuel pump by-pass relay circuit
77 Malfunction detected with power feed to speed control servo solenoids
Source : Jeep Info
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