Author Topic: 1988 W250 TPS sensor (TPS diagnostics)  (Read 6047 times)

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Offline dixiedodge

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1988 W250 TPS sensor (TPS diagnostics)
« on: April 25, 2006, 07:21:42 pm »
I've been getting trouble code 24  (tps sensor). I did the check with the ohm meter and checked the voltage on the wiring. Everything checks out ok but this is the second time I've got this code. Also, there is no check engine light but I am getting a code. It has been idleing funny, up and down but steady, its never the same. Should I replace?
« Last Edit: July 13, 2014, 11:57:50 am by ToxicDoc »
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    Offline DODGEBOYS

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    Re: !988 W250 TPS sensor
    « Reply #1 on: April 26, 2006, 05:05:16 am »
    whats the base voltage / if its off it will set this code
    put your truck info HERE
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    Offline dixiedodge

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    Re: !988 W250 TPS sensor
    « Reply #2 on: April 26, 2006, 04:21:54 pm »
    What do you mean by base voltage? At the battery?
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    Offline DODGEBOYS

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    Re: !988 W250 TPS sensor
    « Reply #3 on: April 26, 2006, 05:46:22 pm »
    NO the minumum voltage the the sensor is suppose to run at / lets say it wants 0.43 volts and its at 0,38 volts / that will pull a code / so if you adjust the BASE idle to bring it into SPECs thats all you need to do
    put your truck info HERE
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    Offline ramcharger422in3

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    Re: !988 W250 TPS sensor
    « Reply #4 on: July 12, 2014, 05:34:46 am »
    I have been researching what to do with regards to the error 24 on my own 1988. Here is what I found that helped me:

    Code 24 will set when the voltage returning from the TPS exceeds 4.7 volts or is less than 0.16 volts. During normal operation, the voltage range for this sensor is usually about 1.3 V with the throttle closed and between 4.0 and 4.5 volts with the throttle wide open. A fault in this that is intermittent is probably due to a loose wire or connector.

    The TPS is used to control the fuel injection system, shift the automatic transmission, and control torque converter lock up. A noisy TPS, or a TPS out of adjustment may cause numerous problems without setting a fault code. See the TPS test and adjustment procedure for problems that do not set a fault code.

    The TPS is located 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. If wiggling the connector sets a fault, carefully clean the terminals of the connector and sensor, then reassemble and repeat the wiggle test.

    TPS circuit tests for vehicles with a hard DTC 24.

    To find the source of the code 24 problem, begin by turning off the ignition switch and disconnecting the TPS harness from the TPS. Turn the ignition switch back on. Connect a digital voltmeter across the two outer wires of the connector. The positive lead of the voltmeter should be on the violet and white wire. The negative lead should be on the black and light blue wire. The voltmeter should read 5 volts. If yes, go to 1; if no go to 2.

    1.   If the TPS connector has 5 volts between the violet-white wire and the black-light blue wire (the two outside terminals), then it will be necessary to test the center wire of the circuit. It is the center wire that delivers the signal to the computer. Connect the voltmeter positive lead to the center wire (orange-dark blue) of the TPS connector and the negative lead to battery ground. The meter should read more than 2.5 but less than 4.9 volts. If it reads zero or 5 volts, disconnect the battery, remove the PCM connector, and check continuity from the TPS connector to pin 23 of the PCM connector.

    2 If the TPS connector does not have 5 volts between the the two outside terminals (violet-white wire and the black-light blue wire), leave the positive lead connected and move the voltmeter negative lead to battery ground. The voltmeter should read 5 volts. If it does, go to 3; if not, go to 4.

    3. If the voltmeter reads 5 volts from the TPS connector (violet and white wire) to the battery, but not to the black and light blue wire in the TPS connector, the ground circuit is bad. Disconnect the battery, remove the PCM connector, and check for continuity from the TPS connector to pin 4 on the PCM connector.

    4. If no wiring problems are found, check the PCM connectors for corrosion, and reconnect. Reconnect the battery and test the circuit again. If the problem still exists, the PCM is probably bad.

    The throttle position sensor, shift lever, and throttle valve cable are critical to proper operation of the transmission. If one or more of these are out of adjustment or if the TPS is noisy, shifting will be erratic. Before performing any adjustments, check the transmission fluid level and sniff the fluid. Do not make any adjustments until the fluid level is correct, and burned fluid has been replaced.

    The service manual says to adjust for 0.8-1.2V at idle. On many trucks, this voltage is too low, resulting in TCC chatter at moderate throttle loads. The TPS is not officially adjustable but the mounting holes are slotted and the body can be rotated slightly. Adjustment is relatively easy, and requires only a digital voltmeter and a few hand tools. A little adjustment goes a long way... 

    TPS wire color code:

    Black = ground
    Orange/dark blue stripe (center pin) = signal
    Purple/white stripe = 5V power
    Testing and adjusting the TPS:

    1.    With the key "OFF", unplug the connector from the TPS.

    2.    Turn the key "on" and insert DVM probes into the connector to reach the connector pins. Short pieces of wire or paper clips can be used to extend the DVM probes for reaching into the connectors.

    3.    Read from the purple wire to the black wire (these should be the outside pins). Power should be 5V with the key "on".

    4.    Turn the key "off" and plug the connector back onto the TPS

    5.    Insert the leads from the digital volt meter into the back of the TPS connector. The DVM negative probe goes into the back of the connector cavity with the black wire. The positive DVM probe goes into the back of the connector cavity with the orange signal wire.

    NOTE:    Push the probes into the rear of the connector until the probe tips reach the metal connector pins.

    6.    Loosen the TPS mounting screws

    7.    With the engine off and key on: Adjust the TPS position for 1.2 to 1.5V on the signal wire with the throttle at the idle position - more voltage makes more TC clutch pressure, too much will set a fault code. Often, adjusting for 1.4 to 1.5V at idle will cure TC clutch chatter under light load conditions. NOTE: The factory setting is 1.2V max, so proceed carefully.

    8.    Tighten the TPS screws, slowly open the throttle to the WOT position and then return return to idle. Watch for voltage jumps - the voltage should change smoothly from the idle value to at least 3.5V at WOT (5 volts is all you should be able to get). If the sensor voltage jumps or drops unexpectedly - replace the sensor or try the filter modification below.

    Hope this helps someone! - Jeff

    Offline TheRamMan

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    Re: 1988 W250 TPS sensor (TPS diagnostics)
    « Reply #5 on: May 25, 2016, 04:47:18 pm »
    I would follow the previous tests in the post. That are pretty much all of the diagnostics you can do on it. Might also try to see if something else is causing the tps to operate funny which is ultimately making the truck run poorly. I have seen problems like that before make guys go crazy. If you narrow it down to this then i would replace it its most likely the original and might be just worn and acting funny. Even if you are getting the right voltages and resistance i would also just do a visual of the wires check for burns, corrosion and possible shorts this could cause the tps to act abnormally.
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    Offline SidWho?

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    Re: 1988 W250 TPS sensor (TPS diagnostics)
    « Reply #6 on: July 21, 2018, 04:15:21 pm »
    Just to add to the great write-up on how to test...paper-clips come in handy instead of trying to force the meter probes in the rear of connector and if everything checks out and code persists, try pulling (wiggle test) the wires from TPS to ecm/pcm connector.
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    Offline MitchUpton

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    Re: 1988 W250 TPS sensor (TPS diagnostics)
    « Reply #7 on: October 29, 2018, 03:13:15 pm »


    I performed this diagnostic the other day (92 Ramcharger, 5.2 MPFI), and got .65v between middle pin and ground. I could move the TPS body just a little bit, and the most I could get the meter to read was .7v, but when I tightened the mounting bolts back down, I got .65v again. Seems like there is no way I'm ever gonna adjust it to get over 1v.

    My service manual doesn't seem to say anything about voltage specs for the TPS at all for my model year and motor.

    That said, a slow progression from idle to WOT yielded a smooth voltage curve from .65v up to about 3.6v

    I'm still having my original issue that made me check the TPS (my overdrive is coming in and out between about 45-50 and light throttle). Not sure how to proceed from here. May check the speed sensor next (wire/connector condition, etc.)

    Mitch
    92 Ramcharger 4wd (5.9 swap, 46rh rebuilt)

     

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