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IMPORTANT. Codes may be different for newer vehicles starting in the late 1990s. See the earlier section.
The power module has an air-cooled resistor which senses incoming air temperature. The logic modules uses this information to control the field current in the alternator. This code applies ONLY to alternators whose voltage is computer regulated. If you lose the feed to keep RAM information stored when the engine's off, you also lose battery voltage sensing. -- Bohdan Bodnar
From the 1995 TRUCK manuals: the trailer towing package includes a transmission coolant temp sensor while the standard package doesn't. This may cause the low (no) voltage indication. -- J.E. Winburn
Matt Rowe: “The throttle postion circuit tells the computer how far the accelerator is depressed. The Throttle Position Sensor (TPS) is on the throttle body on the opposite side of the throttle cable. The connector should have a round rubber cover over the connections. Clear the fault codes, start the car and try jiggling the wires/connectors to try to trip a fault code. Loss of this signal could cause other problems.”
Tom Wand: “Throttle Position Sensors (TPS) will on some early 1990s trucks start to drift high in voltage, there was a problem with these and the idle will not set low enough. Need to replace if it does this. As I recall, the output voltage at idle is 2.4 volts, much above is no good.”
During cranking, the computer will test the current through the injector to see whether there's too much resistance in the injector's path. If there is, code 26 is set.
The problem may be cured with tuner cleaner on the connectors.
For TBI engines, the injector's cold resistance should be between 0.9 and 1.2 ohms (specs vary with year). This is a peak-and-hold injector. With the engine idling the peak period should be about 1.2 milliseconds whereas the hold period will vary. If it's lower than this at idle, then the injector's shorted or there's a defect in the injector driver circuit. (Bohdan Bodnar)
Wade Goldman wrote: In my case, the breather tube leading into the catalytic converter had rusted and become detached. This some how would cause the sensor to read an over rich condition and run crummy. I did not trust the reliability of the weld over a corroded surface and opted for the more expensive route of replacing the converter, breather tube and all.
The Z1 voltage is the voltage of the circuits fed by the autoshutdown relay. This typically includes fuel pump and switched-battery feed to the ignition coil(s). In my Le Baron, the Z1 circuit leaves the power module and splits into two paths: the fuel pump and the positive side of the ignition coil. Internal to the power module is the auto shutdown relay (in my case, it's a sealed box about 1" by 1"). The output voltage is monitored to determine whether the relay responds correctly. I suspect that the ASD relay (and, therefore, the Z1 circuit) also feeds the fuel injector(s) driver(s) and current sensing circuit, but can't prove this.
I've used the Z1 voltage to test for good power connections to the power module. I connected my OTC 500 multimeter from the battery's positive post to the ignition coil's switched battery terminal and measured the voltage drop using the bar graph to monitor peak voltages. Voltage spikes of around 200 mV to 300 mV are ok -- anything more means tv tuner cleaner time (or replacing the power module). Another thing to check is the maximum voltage drop during the priming pulse. With the old power module, I was losing about 2 volts across the circuit; the replacement is losing about 1/4 volt. (Thanks, Bohdan Bodnar)
Unconfirmed correction: The Z1 Circuit is used to feed the engine computer; if it is lost, the delayed turnoff will not occur, and restarting will not go well. I forget but think it is the engine flair (speed flair up upon starting) that is lost. It also feeds the injectors and solenoids and other relays. (Thanks, Tom Wand)
Steve Knickerbocker wrote: Inside your distributor you have two pickups, one is for the ignition and one is to tell the computer where number one cylinder is in its rotation. If you look at the four slotted tangs inside there you will see one has a bigger slot, that's the one that tells the sync pickup what's number one. In other words, the pickup inside the distributor is bad.
Can cause the engine to stop working entirely with no limp-home mode. Note: An anonymous poster wrote, “Code 11 will only be set upon clearing the codes, most commonly by disconnecting the battery. It says in the factory diagnostic manuals that code 11 means no ignition reference signal has been seen since battery disconnect. As soon as the vehicle's engine is cranked, and a reference signal is seen, code 11 will go away immediately on it's own. It also won't be set upon failure of a part such as a hall-effect pick-up plate, or loss of the timing belt. If no reference signal is seen during cranking after a battery disconnect, code 11 will remain. This is a helpful indicator in a no-start condition.” (Chrysler did sometimes change codes depending on the year, so it may be that some of these apply to differentyears.)
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Chrysler, Plymouth, Dodge, and Jeep car, minivan, and truck computer fault codes: how to get them and what to do with them for sensors and troubleshooting.