first time for this to happen, cruising along cold a.m , felt a little tug and BAM! check engine light comes on. off to autozone, they pulled up ( ALPHA) P1870 here is what the printout says, transmission automatic 4-wheel drive indicator (lamp) circuit short to battery, transmission mechanical transfer case 4x4. WTF!! is this another way of saying the tranny is slipping and on it's last leg?. I can accept that it's time for a new built up tranny , 99400k ,390 rwhp 98 A4. thanks in advance for all the feedback.

 

Below is the description of that code from the manual. I won't list the diagnostic procedure that goes with it as it's too long and the format won't transfer. Email me at edbon@adelphia.net and I'll send it.

Circuit Description
The powertrain control module (PCM) monitors the difference between engine speed and transmission output speed. In D3 drive range with the TCC engaged, the engine speed should closely match the transmission output speed. In D4 drive range, with the TCC engaged, the TCC slip speed should be -20 to +50 RPM.

When the PCM detects excessive TCC slip when the TCC should be engaged, then DTC P1870 sets. DTC P1870 is a type B DTC.

Conditions for Running the DTC
No TP sensor DTCs P1120 or P1220.
No VSS assembly DTCs P0502 or P0503.
No TCC solenoid valve DTC P0740.
No 1-2 SS valve DTC P0753.
No 2-3 SS valve DTC P0758.
No 3-2 SS valve assembly DTC P0785.
No TFP manual valve position switch DTC P1810.
No TCC PWM solenoid valve DTC P1860.
No MAF DTCs.
The engine speed is greater than 450 RPM for 5 seconds.
The engine is not in fuel cutoff.
The engine torque is 68-542 N·m (50-400 lb ft).
The engine vacuum is 0-105 kPa (0-15 psi).
The TP angle is 20-99 percent.
The vehicle speed is 48-131 km/h (30-82 mph).
The engine speed is 1,500-3,000 RPM.
The speed ratio is 0.69-0.88, speed ratio is engine speed divided by the transmission output speed.
The gear range is D4.
The commanded gear is not 1st gear.
The TFT is 20-150°C (68-302°F).
The shift solenoid performance diagnostic counters are zero.

Conditions for Setting the DTC
DTC P1870 sets if the following conditions occur for three TCC cycles.

The TCC is commanded ON for 5 seconds.
The TCC is at 40 percent duty cycle for 5 seconds.
The TCC slip speed is 130-800 RPM for 7 seconds.

Important
The following actions may occur before the DTC sets.


If the TCC is commanded ON for 5 seconds, the TCC is at 40 percent duty cycle for 5 seconds, the TP angle is 20-99 percent and the transmission slip counter has incremented to either 1 or 2, out of 3 to increment the fail counter for the current ignition cycle, then the following slip conditions and actions may increment the fail counter for the current ignition cycle: These conditions must occur sequentially.
Condition 1
If the TCC slip speed is 130-800 RPM for 7 seconds, then the PCM will command maximum line pressure and freeze shift adapts from being updated.

Condition 2
If Condition 1 is met and the TCC slip speed is 130-800 RPM for 7 seconds, then the PCM will command the TCC Off for 1.5 seconds.

Condition 3
If Condition 2 is met and the TCC slip speed is 130-800 RPM for 7 seconds, then the fail counter on the current ignition cycle is incremented.

The above slip conditions and actions may be disregarded if the TCC is commanded OFF at any time as a result of a driving maneuver, sudden acceleration or deceleration.

Action Taken When the DTC Sets
The PCM illuminates the malfunction indicator lamp (MIL) during the second consecutive trip in which the Conditions for Setting the DTC are met.
The PCM commands maximum line pressure.
The PCM inhibits TCC engagement.
The PCM inhibits 4th gear if the transmission is in hot mode.
The PCM freezes transmission adapt functions.
The PCM records the operating conditions when the Conditions for Setting the DTC are met. The PCM stores this information as Freeze Frame and Failure Records.
The PCM stores DTC P1870 in PCM history during the second consecutive trip in which the Conditions for Setting the DTC are met.
Conditions for Clearing the MIL/DTC
The PCM turns OFF the MIL during the third consecutive trip in which the diagnostic test runs and passes.
A scan tool can clear the MIL/DTC.
The PCM clears the DTC from PCM history if the vehicle completes 40 warm-up cycles without an emission-related diagnostic fault occurring.
The PCM cancels the DTC default actions when the ignition switch is OFF long enough in order to power down the PCM.

Diagnostic Aids
Bronze material found in the transmission oil pan may indicate stator shaft bushing wear. If bushing wear is suspected, inspect the stator shaft and the input, turbine, shaft for damage.
Refer to Symptoms - Automatic Transmission for more information.

 

Patches; email sent

 

can't seem to understand where they come up with this ???


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I think Patches has you covered!