Just bought 97 C5 and drove 20 miles and got check engine light, Dtc was P1870...read all the threads on P1870 problems...took to transmission guru, he said transmission was working great, no torque converter problems, new valving was already done, he said tranny was working as it should but he also got a P1571 code coming up at the same time as the P1870 so he thought it might be a wheel sensor giving false info back to PCM? Or, maybe a different transmission or differential was installed at some point in the life of the car? Any new ideas?

 

DTC P1870 Transmission Component Slipping



DTC P1870 Range Reference Thumbnail 4L60-E Range
Gear
Shift Solenoid
TCC Solenoid
TCC PWM Solenoid
2-4 Band
Forward Clutch
3-4 Clutch
Torque Converter Clutch

1-2
2-3

Overdrive
4th
ON
OFF
ON
90% (ON)
Applied
Applied
Applied
Applied


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 +30 RPM. The table above indicates solenoid states and transmission components that apply, during 4th gear, with the TCC commanded ON.

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 Setting the DTC
DTC P1870 sets if the following conditions are met for three TCC cycles with reported excessive TCC slip conditions, two consecutive times.

No TP Sensor DTCs P0122 or P0123.
No VSS Assy. DTCs P0502 or P0503.
No TCC Sol. Valve DTC P0740.
No 1-2 SS Valve DTC P0753.
No 2-3 SS Valve DTC P0758.
No 3-2 SS Valve Assy. DTC P0785.
No TCC PWM Sol. Valve DTC P1860.
The engine speed is greater than 450 RPM for 8 seconds.
Not in fuel cutoff.
The vehicle speed is 56-105 km/h (35-65 mph).
The speed ratio is 0.67-0.9 (the speed ratio is the engine speed divided by the output speed).
The engine speed is 1200-3500 RPM.
The engine torque is 40-400 lbs ft.
The gear range is D4.
Not in 1st gear
The TP angle is 10-50%.
The TFT is between 20-130°C (68-266°F).
TCC is commanded On for 5 seconds.
The TCC is at maximum apply for 5 seconds.
The shift solenoid performance diagnostic counters are zero.
The TCC slip speed is 150-800 RPM.
All conditions met for 7 seconds.
Action Taken When the DTC Sets
The PCM illuminates the Malfunction Indicator Lamp (MIL).
The PCM inhibits TCC engagement.
The PCM commands maximum line pressure.
The PCM inhibits 4th gear if the transmission is in hot mode.
The PCM freezes shift adapts from being updated.
DTC P1870 stores in PCM history.
Conditions for Clearing the MIL/DTC
The PCM turns OFF the MIL after three consecutive trips without a failure reported.
A scan tool can clear the DTC from the PCM history. The PCM clears the DTC from the PCM history if the vehicle completes 40 warm-up cycles without a failure reported.
The PCM cancels the DTC default actions when the fault no longer exists and the ignition is OFF long enough in order to power down the PCM.
Diagnostic Aids
Internal transmission failures could set a DTC P1870.
A TFP Valve Position Switch malfunction could set a DTC P1870.
----------------------------------------------------------------
DTC P1571 Traction Control Torque Request Circuit




Circuit Description
The PCM supplies 5.0 volts on the Desired Torque circuit to the Electronic Brake and Traction Control Module (EBTCM). The EBTCM toggles this 5.0 volt signal to a ground in order to produce a duty cycle signal. The signal is proportional to the amount of engine output torque reduction requested by the EBTCM. The EBTCM supplies this signal when it detects a wheel slip. In order to reduce engine output torque, the PCM reduces the amount of spark advance and in some cases the PCM disables a number of fuel injectors. This diagnostic test checks for a Desired Torque signal failure. If the PCM does not receive the Desired torque signal this DTC sets.

Conditions for Setting the DTC
The traction control has not failed.
The engine speed is greater than 500 RPM for 20 seconds.
The desired torque signal is not received by the PCM for 3 seconds.
Action Taken When the DTC Sets
The powertrain control module (PCM) stores the DTC information into memory when the diagnostic runs and fails.
The malfunction indicator lamp (MIL) will not illuminate.
The PCM records the operating conditions at the time the diagnostic fails. The PCM stores this information in the Failure Records.
Conditions for Clearing the MIL/DTC
A last test failed, or the current DTC, clears when the diagnostic runs and does not fail.
A history DTC clears after 40 consecutive warm-up cycles, if failures are not reported by this or any other emission related diagnostic.
Use a scan tool in order to clear the MIL/DTC.
Diagnostic Aids

Important
Do not perform this diagnostic procedure if the customer's concern is not related to the ABS and/or the Traction Control system(s).


The following may cause an intermittent:

Mis-routed harness
Rubbed through wire insulation
Broken wire inside the insulation

 

By the way you can check all the codes on the car by using the On Board Diagnostics just by pushing the buttons on the IP. The only scanner that gives you this much info is the GM Tech 2 and the only one that does more is the Tech 2.

There is a TSB on a persistent P1571 History code on the 97s.
History DTC P1571 Stored and Will Not Clear #PI00219 - (Jul 2, 2002)

History DTC P1571 Stored and Will Not Clear
.
When servicing the vehicle with the VIN you entered, the following diagnosis might be helpful if the vehicle exhibits the described symptoms.
Condition/Concern:

Vehicle may have a DTC P1571 [ASR (Automatic Slip Regulation) Desired Torque Circuit] stored in history that cannot be cleared. DTC C1277 (Requested Torque Signal CKT Malfunction) is NOT present and there is No Service Vehicle Soon lamp or powertrain related lamps on.
Recommendation/Instructions:

This is a normal condition. All 1997 YBs will have a DTC P1571 stored as history in the PCM that cannot be cleared. If P1571 is current, follow the trouble table in SI Document Number 101551. It should be noted that the schematic in this document incorrectly lists a ckt 449 dk blu/wht and calls it Real Time Dampening. This ckt is not present and should be ignored for both 97 and 98 (Document Number 203769) model year SI. A Service Information Update has been submitted.


You should check to see if the diff gear ratio has been changed. Here is another TSB describing how P1870 will be flagged if the diff is different.


97-05 Chevrolet Corvette 4L60E/4165E P0894/P1870 After Ring and Pinion Replacement kw aftermarket axle converter DTC gear repair slip transmission P1870 P0894 #PIP3257 - (Dec 7, 2004)

97 - 05 Chevrolet Corvette 4L60E/4L65E P0894/P1870 After Ring and Pinion Replacement.


The following diagnosis might be helpful if the vehicle exhibits the symptom described in the PI.
Condition/Concern:

he 4L60E/4L65E automatic transmission may experience a condition of DTC P1870/P0894 after the installation of an incorrect ring and pinion gear ratio.
Recommendation/Instructions:

Install the correct gear ratio ring and pinion.



Bill

 

Thanks for the responses...I'm going to check the gear ratio this weekend. Can the PCM be reprogrammed for the differential ratio if it is different than what came in the car? Lets say that someone put a 3:15 in instead of a 2:73.
Keith

 

"Can the PCM be reprogrammed for the differential ratio if it is different than what came in the car?"
---------------------------------------------------
Yes.

 

Thanks for the prompt responses!

 

Checked the ratio and it looks like someone put a 3:47 differential in it. Will a hypertech or diablo programmer allow me to correct the situation by reprogramming the PCM?

 

I had the same issue when changing to the 3:42 gears. I took it to a shop. They had to adjust the slip table on their hp tuners software so it wouldn't falsely think it was slipping anymore. do a search for the code 'p1870' here or 'slip table'. It should give you more info if you're going to do it yourself.

 

Correction, there is a 3:42 differential in it. What did you set your slip table to? What worked for you 100/100 or ? Will the Preditor or hypertech work or will I have to find someone with a HP Tuner? I'm a do-it-yourselfer but, I don't have these tools...(yet). Can the stealership do this or will I have to find a Vette Tech? I'm in SE North Carolina and good vette tech's are scarce as virgin's in Vegas.

 

I didn't do it myself, so I don't know what they tuned it to.

Your best bet is to make a thread in the tuning section. They can answer all of those questions about the various programmers and settings on the slip table. The dealership will not do it though.

Here is my thread in that section from before that may help with some of your questions :
http://forums.corvetteforum.com/c5-s...ing-p1870.html

 

Changing the programming for the gear ratio can be done with a Hypertech Programmer. Its one of the few things you can do with them.

Bill

 

Thanks to all of you who responded on this thread...I really appreciate the comments and great information. I found a performance tuning shop within 60 miles of me and am taking it there this week to see if they can reprogram the PCM.

 

if you're talking about where you just enter the gear ratio, they had done that at first on mine, but that didn't fix the p1870 code. They then had to go in and change the slip table as well.

 

Bill; unless things changed recently- the Hypertech was the lone device that failed at C5 rear axle ratio changes. It's didn't make all the changes needed... and the P1870 code was still setting.