check engine light

[AVILES]

The check engine light went on and the computer said it was code p0204 which is fuel injector circuit condition- injector #4, what can I do to fix it, do I need to replace the injectors or is it more on the electrical part? Any ideas help, thanks

 

[SteelHeadz]

Check the injector wiring first. If it checks out good, swap the injector with another good injector from a different cylinder. If it follows, the injector is bad, if it doesn't, the problem is in the wiring or the PCM.

 

[AVILES]

i did the second step you told me and the problem is still there and the same code pops up, as to wiring they seem fine i disconnected each fuel injector harness one at a time and you can tell they are all working. im out of choices and have no clue on what it could be, it seems to run good sometimes and for a while then out of nothing it starts to act as if it wanted to die but doesnt and it backfires, usually un hills or when ever the rpms are low and you need to accelerate.

 

[AVILES]

ok my sisters impala had a similar problem once were she started to loose power little by little to the point were the car wouldnt want to start and it ended up being the catalytic converter. also my brother told me it could be that, so i was wondering if it could be that and what or why that code would show up. because if it is the cat i was thinking of just geting a saw and taking it off, at least so i can drive it back from austin to el paso.

 

[SteelHeadz]

I doubt that it's the catalytic converter otherwise there will be a catalytic efficiency dtc or an O2 sensor or even a misfire condition dtc. I would suspect that the injector is intermittently shutting down. Measure the resistance on the injector in question. The resistance should be between 10.0- 16.0 Ohms, if not, replace the injector. If it is, measure the resistance across the #4 injector driver circuit. If the resitance is below 5 Ohms the PCM is at fault, if not, check the injector #4 driver circuit for an open circuit. Dark green /Black= ASD Relay output, Light blue/Brown= Driver circuit to PCM. Also check the ASD relay circuits and make sure the voltage on the ASD output cycles high and low.

 

[Dirt Toy]

Get some spray electric connection cleaning. remove the three cable plug in above the battery, clean both sides. remove top on fuse box in front of battery, remove each fuse and use cleaner.

This will reset your pcm, and it takes about 50 miles to get reset.

run some fuel injector cleaner thru you gas tank.

this will rule out electrical connection.

follow troubleshooting of the direct injector problem from other suggestion.

the problem pcm on jeeps is that weird coded that is not directly related to
error code.

I have a friend that his jeep that was having bad cylinder one and the jeep would not run right. He would reset pcm and he could drive for a while.

another friend that went so far that he replace the pcm and the problem was connection problem.

Good Luck solving the problem.

 

[AVILES]

just to make sure injector number 4 would be the one at the end of the engine right? by the firewall

 

[AVILES]

ok so i disconnected the battery for about 5 hours, and before connecting it i swapped the horn relay with the asd relay. when i turned it on the check engine light was off, so i drove it for probably 3 miles on regular streets and about 3 miles highway and it ran and accelerated good but then once again after a while the check engine light went on again and it started to loose acceleration power. ill take it to autozon tomorrow to run the codes test but im thinking it will be the same code as before. any ideas on what it could be?

 

[AVILES]

ok i checked the risistance for all the injectors and it reads about, 12.6 to 12.9ohms on all 4 injectors. how would i check the driver circuit for an open circuit to the pcm, or that that was advised to me earlier? thanks

 

[SteelHeadz]

The light blue/brown wire to the injector is the driver circuit from the PCM. Check the resistance of this circuit from the injector connector to the PCM. A high resistance would indicate a short to ground or short to voltage. Make sure the connector on the injector and the connector on the PCM is disconnected from their respective components to get an accurate test result.

 

[AVILES]

another thing, could it be a spark plug or a spark plug cable by any chance?

 

[SteelHeadz]

Possibly. What was the DTC?. Same test, swap the spark plug from another cylinder and see if the dtc follows. An example would be, P0301 is a misfire on #1 cylinder, P0302 is #2 cyl. etc. If it doesnt follow, swap the ignition wire and re check the dtc.

 

[AVILES]

well i got a p0204, ill change the spark plug and see what happens!!!

 

[SteelHeadz]

The P0200 code still refers to the injector circuits. The absence of the P0300's means there's no misfire detected with the injector dtc. I'm thinking the issue is still within the input circuit of the injector.
MODES OF OPERATION

As input signals to the powertrain control module (PCM) change, the PCM adjusts its response to the output devices. For example, the PCM must calculate different injector pulse width and ignition timing for idle than it does for wide open throttle (WOT)
The PCM will operate in two different modes: Open Loop and Closed Loop.
During Open Loop modes, the powertrain control module (PCM) receives input signals and responds only according to preset PCM programming. Input from the oxygen (O2S) sensors is not monitored during Open Loop modes.
During Closed Loop modes, the PCM will monitor the oxygen (O2S) sensors input. This input indicates to the PCM whether or not the calculated injector pulse width results in the ideal air-fuel ratio. This ratio is 14.7 parts air-to-1 part fuel. By monitoring the exhaust oxygen content through the O2S sensor, the PCM can fine tune the injector pulse width. This is done to achieve optimum fuel economy combined with low emission engine performance.
The fuel injection system has the following modes of operation:

• Ignition switch ON
• Engine start-up (crank)
• Engine warm-up
• Idle
• Cruise
• Acceleration
• Deceleration
• Wide open throttle (WOT)
• Ignition switch OFF

Based on this modes of operation, the symptom seems to occur after it has reached the closed loop mode since you drove it for about 6 miles before the DTC (P0204) came back.
ENGINE WARM-UP MODE

This is an Open Loop mode. During engine warm-up, the powertrain control module (PCM) receives inputs from:

• Battery voltage
• Crankshaft position sensor
• Engine coolant temperature sensor
• Intake manifold air temperature sensor
• Manifold absolute pressure (MAP) sensor
• Throttle position sensor (TPS)
• Camshaft position sensor signal (in the distributor)
• Park/neutral switch (gear indicator signal - auto. trans. only)
• Air conditioning select signal (if equipped)
• Air conditioning request signal (if equipped)

Based on these inputs the following occurs:

• Voltage is applied to the fuel injectors with the ASD relay via the PCM. The PCM will then control the injection sequence and injector pulse width by turning the ground circuit to each individual injector on and off.
• The PCM adjusts engine idle speed through the idle air control (IAC) motor and adjusts ignition timing.
• The PCM operates the A/C compressor clutch through the A/C compressor clutch relay. This is done if A/C has been selected by the vehicle operator and specified pressures are met at the high and low - pressure A/C switches. Refer to Heating and Air Conditioning for additional information.
• When engine has reached operating temperature, the PCM will begin monitoring O2S sensor input. The system will then leave the warm-up mode and go into closed loop operation.

IDLE MODE

When the engine is at operating temperature, this is a Closed Loop mode. At idle speed, the powertrain control module (PCM) receives inputs from:

• Air conditioning select signal (if equipped)
• Air conditioning request signal (if equipped)
• Battery voltage
• Crankshaft position sensor
• Engine coolant temperature sensor
• Intake manifold air temperature sensor
• Manifold absolute pressure (MAP) sensor
• Throttle position sensor (TPS)
• Camshaft position sensor signal (in the distributor)
• Battery voltage
• Park/neutral switch (gear indicator signal - auto. trans. only)
• Oxygen sensors
• Power steering pressure switch (2.5L engine only)

Based on these inputs, the following occurs:

• Voltage is applied to the fuel injectors with the ASD relay via the PCM. The PCM will then control injection sequence and injector pulse width by turning the ground circuit to each individual injector on and off.
• The PCM monitors the O2S sensor input and adjusts air-fuel ratio by varying injector pulse width. It also adjusts engine idle speed through the idle air control (IAC) motor.
• The PCM adjusts ignition timing by increasing and decreasing spark advance.
• The PCM operates the A/C compressor clutch through the A/C compressor clutch relay. This is done if A/C has been selected by the vehicle operator and specified pressures are met at the high and low - pressure A/C switches. Refer to Heating and Air Conditioning for additional information.

On 2.5L 4 - cylinder engines, a power steering pressure switch is used to supply an input to the PCM when steering pump pressure is high. This will raise engine speed. Refer to Power Steering Pressure Switch in this group for additional information. The 4.0L 6 - cylinder engine does not use this switch.
CRUISE MODE

When the engine is at operating temperature, this is a Closed Loop mode. At cruising speed, the powertrain control module (PCM) receives inputs from:

• Air conditioning select signal (if equipped)
• Air conditioning request signal (if equipped)
• Battery voltage
• Engine coolant temperature sensor
• Crankshaft position sensor
• Intake manifold air temperature sensor
• Manifold absolute pressure (MAP) sensor
• Throttle position sensor (TPS)
• Camshaft position sensor signal (in the distributor)
• Park/neutral switch (gear indicator signal - auto. trans. only)
• Oxygen (O2S) sensors

Based on these inputs, the following occurs:

• Voltage is applied to the fuel injectors with the ASD relay via the PCM. The PCM will then adjust the injector pulse width by turning the ground circuit to each individual injector on and off.
• The PCM monitors the O2S sensor input and adjusts air-fuel ratio. It also adjusts engine idle speed through the idle air control (IAC) motor.
• The PCM adjusts ignition timing by turning the ground path to the coil on and off.
• The PCM operates the A/C compressor clutch through the clutch relay. This happens if A/C has been selected by the vehicle operator and requested by the A/C thermostat.
• The Up-shift Indicator Lamp is operated (manual transmission only)

ACCELERATION MODE

This is an Open Loop mode. The powertrain control module (PCM) recognizes an abrupt increase in throttle position or MAP pressure as a demand for increased engine output and vehicle acceleration. The PCM increases injector pulse width in response to increased throttle opening.
DECELERATION MODE

When the engine is at operating temperature, this is an Open Loop mode. During hard deceleration, the powertrain control module (PCM) receives the following inputs.

• Air conditioning select signal (if equipped)
• Air conditioning request signal (if equipped)
• Battery voltage
• Engine coolant temperature sensor
• Crankshaft position sensor
• Intake manifold air temperature sensor
• Manifold absolute pressure (MAP) sensor
• Throttle position sensor (TPS)
• Camshaft position sensor signal (in the distributor)
• Park/neutral switch (gear indicator signal - auto. trans. only)
• Vehicle speed sensor

If the vehicle is under hard deceleration with the proper rpm and closed throttle conditions, the PCM will ignore the oxygen sensor input signal. The PCM will enter a fuel cut-off strategy in which it will not supply a ground to the injectors. If a hard deceleration does not exist, the PCM will determine the proper injector pulse width and continue injection.
Based on the above inputs, the PCM will adjust engine idle speed through the idle air control (IAC) motor.
The PCM adjusts ignition timing by turning the ground path to the coil on and off.
WIDE OPEN THROTTLE MODE

This is an Open Loop mode. During wide open throttle operation, the powertrain control module (PCM) receives the following inputs.

• Battery voltage
• Crankshaft position sensor
• Engine coolant temperature sensor
• Intake manifold air temperature sensor
• Manifold absolute pressure (MAP) sensor
• Throttle position sensor (TPS)
• Camshaft position sensor signal (in the distributor)

During wide open throttle conditions, the following occurs:

• Voltage is applied to the fuel injectors with the ASD relay via the PCM. The PCM will then control the injection sequence and injector pulse width by turning the ground circuit to each individual injector on and off. The PCM ignores the oxygen sensor input signal and provides a predetermined amount of additional fuel. This is done by adjusting injector pulse width.
• The PCM adjusts ignition timing by turning the ground path to the coil on and off.
• The Up-shift Indicator Lamp is operated (manual transmission only)

With this information, we can eliminate some of the variables thats not a possible source of the DTC. From what i see, the possible components in question here would be as follows:

Injector pulse circuit from the PCM(wiring)
CKP or the reference tone ring of the sensor
CMP or its reference tone ring
PCM
Since you have already swapped the injector from another cylinder and the DTC is STILL in the same position, i would eliminate the injector itself to be the possible cause. Out of all the sensors involved in the modes of operation that's relevant to the function and command of the fuel injection system, I would also eliminate the O2 sensors, Map sensor, IAT sensor, safety neutral switch, ECT sensor, battery voltage, TPS, powersteering pressure switch from the possible cause of the DTC.
If i was to troubleshoot this issue, i would start with the wiring for the process of elimination.
I can walk you through the wiring diagram if you wish but you have to do the dirty work and find the wiring involved on the injector #4 circuit. The PCM wiring can be intimidating but if you follow the wiring color code and with the use of a DMM(digital multimeter) , you should be able to find and verify that the wiring passes the test.

 

[AVILES]

it looks like the wires that go from the computer to the injector harness are all good, they all seem to have resistance, all four injectors seem to be right, and i changed sparkplugs and wires yesterday, and it keeps on doing the same thing except it seems like it is doing it more often, does that mean that the computer is bad, and is their a way to check it?, also it smells alot like gas when the engine is running and it looks like it is trowing out white smoke. thank you