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Thread: ZF 4HP24, where did I messed up ?

  1. #1
    Join Date
    May 2018
    Location
    France
    Posts
    77
    My Cars
    1986 325i, 1991 850i, Z4

    ZF 4HP24, where did I messed up ?

    Hi,

    A month ago I cleaned my ZF 4HP24 valve body to get rid of harsh gear changes. It has worked well but I've soon noticed gearbox fluid on the floor after leaving the car for a while, but the gearbox worked perfectly.
    This came from the o-ring around the plug for the electrical connector so I've replaced it, topped up the transmission fluid and went for a drive. The 2nd gear took a lot of time to come and it seemed clear that the car was not behaving properly which led to a Trans fail safe program appearing in the MID with a yellow check in the instrument cluster. Thinking that this could be due to low fluid level, I added some, unplug the battery for an hour or so and went for a drive. The error came back. I've done a stomp test and got 1235 but didn't find what it meant.

    Then I thought that it could just be an unplug connector to a solenoid. So I took it apart once more, checked all connections (which were good) and resistance on the different pins: all of them are normal except for the output speed sensor. I got 312ohms instead of 265 ohms. I've tried it again with the same result but the TFS error took a bit more time to come: The first gear reved a lot higher than normal and when it finally got to 2nd gear it kept dropping back to 1st then back to 2nd and then again 1st and finally in TFS mode. Could this be the output speed sensor ?

    I've now took it apart again to check the solenoids. They are all normal, except the MV-5 which had some dirt in the filter (it did not look like metal), could this be the cause or should I look for something else ? Didn't the MV-5 was for the reverse gear only ?
    And where did I went wrong for this error to appear ?

    Thanks for your help

  2. #2
    Join Date
    Jan 2005
    Location
    Japan
    Posts
    54,654
    My Cars
    11/88 E32 750iL+98 E36M3
    here is a link with test data for all the valves and the resistance in ohms http://parts-at.ru/wp-content/upload...Tech-Guide.pdf
    MV-5 is for the line pressure control

    code 1235 is an undefined code https://www.bimmerforums.com/forum/s...omp-Test-Codes

    http://forum.roadfly.com/threads/939...-M70-code-1235
    copied from the RF thread:
    1991 M70 code 1235

    Well, I'm going to hazard a guess that it is something being returned by the A/C or heater system. Since 1234 and 1237 are both A/C related, and yours is in between those two numbers, I'm interpolating your 1235 (but who knows what evil lurks in the minds of E31 design engineers).

    Motronic Codes:
    Early systems
    Early systems (Motronic 1.1 only, I think) flash the fault codes automatically. If the check engine light comes on, leave the key in the On position, but dont start the car. The check engine light will begin to flash the code after about 3 seconds. The interval is about 1 second. There aren't many codes on this system
    1 flash......Air flow sensor malfunction.
    2 flashes....Oxygen sensor malfunction.
    3 flashes....Coolant Temp. malfunction.
    4 flashes....Throttle switch malfunction.
    More detail on these early systems can be found in the Bentley manuals.
    Late 1980's systems. Motronic 1.3
    The fault codes for these systems will appear on the check engine light when you turn the ignition key to the On position (but dont start it), then: fully depress the accelerator pedal, then fully release it. Repeat the depress,release cycle 5 times fairly quickly, but not too fast. It should be completed in a few seconds. What you are doing here is clicking the wide open throttle switch then the idle switch each 5 times. This signals the Motronic unit to send the fault codes by flashing the check engine light. You should see the light flash once then it will start flashing the 4 digit codes. If there are no faults, you should see the 1444 code (and 2444 if you have a 12 cylinder). The codes appear as a series of flashes for each digit. The flashes indicating one digit are about 1 second apart, the next digit appears after a couple second interval. The rest of the fault codes appear in Table 1 below.
    The later systems up to ~ 1995 (Motronic 3.x)
    The fault codes appear in the same way as for the Motronic 1.x systems listed above, but it is much trickier to get them to appear. The timing with which you turn the key then depress and release the accelerator pedal is much more critical. You have to depress and release the pedal 5 times, rhythmically, but much faster than for the earlier system. It usually takes a few tries to get it right.
    The very latest systems (1995 on) Fault codes are not available through the check engine light.

    Table 1. The Motronic Fault Codes.
    Malfunctioning System. Fault Code Comments. DME Control Unit
    1211 Air Mass/Volume Sensor
    1215 Throttle Potentiometer
    1216 Output Stage, Group 1
    1218 Output Stage, Group 2
    1219 EGO(O2) Sensor 1
    1221 EGO(O2) Sensor 2
    1212 Lambda Control 1
    1222 Lambda Control 2
    1213 Coolant Temp. Sensor
    1223 Intake Air Temp. Sensor
    1224 Knock Sensor 1
    1225 not present on V12 Knock Sensor 2
    1226 not present on V12 Knock Sensor 3
    1227 not present on V12 Knock Sensor 4
    1228 not present on V12 Battery Voltage/DME Main Relay
    1231 Throttle Idle Switch
    1232 Throttle WOT Switch
    1233 Speedometer A Signal
    1234 A/C Compressor cut off
    1237 A/C Compressor
    1242 Crankshaft Pulse Sensor
    1243 Camshaft Sensor
    1244 Intervention AEGS
    1245 Ignition Secondary Monitor
    1247 Fuel Injector 1 (or group 1)
    1251 Fuel Injector 2 (or group 2)
    1252 Fuel Injector 3
    1253 Fuel Injector 4
    1254 Fuel Injector 5
    1255 Fuel Injector 6
    1256 Fuel Injector 7
    1257 Fuel Injector 8
    1258 Fuel Pump Relay Control
    1261 Idle Speed Actuator
    1262 Purge Valve
    1263 EGO Heater
    1264 Fault Lamp (check engine)
    1265 VANOS
    1266 Air Pump Relay Control
    1267 Ignition Coil 1
    1271 Ignition Coil 2
    1272 Ignition Coil 3
    1273 Ignition Coil 4
    1274 Ignition Coil 5
    1275 Ignition Coil 6
    1276 Ignition Coil 7
    1277 Ignition Coil 8
    1278 Control Unit Memory Supply
    1281 Fault Code Memory
    1282 Fuel Injector Output Stage
    1283 Knock Control test Pulse
    1286 No Failures
    1444 For 12 cylinder models, there are additional codes for the second Motronic unit. These codes are the same as above, but the first digit (1) is replaced by 2.
    Last edited by shogun; 05-13-2018 at 05:58 PM.
    Shogun tricks and tips for the E32 series are HERE!

  3. #3
    Join Date
    May 2018
    Location
    France
    Posts
    77
    My Cars
    1986 325i, 1991 850i, Z4
    Thanks for your reply, I've already read this post about the 1235 code and it could be in my case linked to a malfunctionning AC.
    For the transmission itself I think that I will change the output speed sensor, because it's the only thing that reads a wrong value (around 315 instead of 265 ohms), do you think it could cause the TFS and the gearbox slipping from 2nd to 1st ?

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