Mechanics

CHEVY P1870

1997 Chevrolet Astro

Transmission problem
1997 Chevy Astro 6 cyl Two Wheel Drive Automatic 160215 miles

Hi I have been dealing with this problem for quite some time. The transmission seems to shift perfectly until that P1870 code comes back and then switches to high pressure mode causing the trans to shift real hard in second. It happens only when your light on the gas. I was trying to pass NYS inspection but couldnt. I FINALLY figured out that if I drove the car below 45, the light would not come on AT ALL. Passed inspection(Completed OBD 2 drive cylces). I have installed a reman valve body with no luck on fixing or band-aiding the problem. I hear that the code is caused by bad brass seals inside the transmission and it needs to be replaced. Is that true? I dont want to change a trans when it seemingly is ok. I did have a good measure of brass in the pan though along with a bunch of tiny round clear balls. I changed the fuild a couple times to flush it out. I thought the P1870 code was because the torque converter was sensed to be slipping but the code ONLY COMES ON ABOVE 45 WHILE CRUISING. Could it be a sensor? There is definately no slipping then because Im not even accerlating. Also definately feels like there is no slipping during acceleration. Any help would be appreciated to solve this head ache once and for all. OHH. I even swapped PCM's with another van-with no MIL light on (no problems) because my transmission guy told me it was my PCM but he was wrong. It did not work either.
Avatar
Bralden
October 28, 2010.



There are many possibilities for causing this code. With the amount of miles on the vehicle, it makes all of the possibilities, possible. Obviously the valve body and PCM were not the cause, but they were the easiest to eliminate, as the others require transmission removal at a minimum. The clear balls in the pan, that is mysterious, I wonder if they weren't fed down the fill tube. As far as the debris in the pan, was it black in color? I believe one of the possibilities for cause, was pump bushing wear, those I think were bronze, and that turns up black in the pan. To isolate it to torque converter slippage, you would almost need a scan tool that could monitor TCC slip speed data. There are a couple GM service bulletins that I will send your way.

#01-07-30-023B: Harsh 1-2 Upshift, SES, MIL, or CEL Illuminated, DTC P1870 Set (Replace Valve Body) - (Mar 22, 2002)

Subject: Harsh 1-2 Upshift, SES, MIL, or CEL Illuminated, DTC P1870 Set (Replace Valve Body)

Models: 1996 Buick Roadmaster

1996 Cadillac Fleetwood

1999-2000 Cadillac Escalade

1996-2000 Chevrolet Camaro, Corvette

1996-2000 Pontiac Firebird

1996-2000 Chevrolet and GMC Light Duty Truck Models

1996-2000 Oldsmobile Bravada

with 4L60-E Automatic Transmission (RPO M30)

Built Prior to January 15, 2000 (Julian Date 0015)

This bulletin is being revised to update VIN Breakpoint Date information and revise the Parts Information table. Please discard Corporate Bulletin Number 01-07-30-023A (Section 07 -- Transmission/Transaxle).

Condition
Some customers may comment on a harsh 1-2 upshift and the Check Engine Light or Service Engine Soon indicator is illuminated.

Diagnosis

Typically, these vehicles will have been driven more than 32,000 km (20,000 mi) before this condition occurs.

The scan tool may show a DTC P1870 set as a history code.

A harsh 1-2 shift or DTC P1870, caused by wear in the control valve body, may be difficult to duplicate when the transmission temperature is below 93 °C (200 °F).

Cause
The condition may be due to wear in the control valve body. This wear occurs in the bore that contains the TCC isolator and regulator valves, and results in poor, or no, TCC apply.

Important: • DTC P1870 is a type B code. The conditions for setting the P1870 DTC must occur on TWO CONSECUTIVE TRIPS (ignition cycles, with a drive cycle) before setting a P1870 history code.

• When the conditions for setting DTC P1870 are met (first trip), the PCM commands maximum line pressure and harsh 1-2 shifts are the result.

• This may result in a harsh 1-2 shift with no history code if the conditions for setting the DTC required for the second trip are not met, on two consecutive trips (Ignition cycles, with a drive cycle).

• When the conditions for setting the DTC are met, on the second consecutive trip, a DTC P1870 is stored as a history code.

• When the P1870 code is stored, the PCM will turn on the Service Engine Soon (SES), Check Engine Light (CEL), or Malfunction Indicator Lamp (MIL).

Correction
Install a control valve body with the revised TCC regulator and isolator valves. Refer to the Parts Information table below. These valves are used in all transmissions produced after January 15, 2000 (Julian Date 0015), and all of the service parts currently available through GMSPO contain revised TCC regulator and isolator valves.

Important: If all of the following conditions are true, it is not necessary to rebuild the transmission or to replace additional transmission components beyond the control valve body.

• Transmission operation is normal before the transmission reaches operating temperature, or before DTC P1870 is set (no slips, flares, or missing gears).

• The torque converter is not blue or overheated.

• The transmission fluid is not burned or has no burned odor.

• The transmission fluid pan contains no abnormal debris (clutch material, bronze, brass, or metal fragments).

Parts Information
Model Year
Vehicle Platform
Engine (RPO)
Transmission (RPO)
Transmission Broadcast Code
P/N

1996
S Truck
2.2L

(LN2)
4L60-E

(M30)
SAD
24217855

1996
C Truck

(Mexico)
5.7L

(LO5)
4L60-E

(M30)
CPD
24217856

1996
C/K Truck

G Van
5.0L

(L30)
4L60-E

(M30)
CCD, CFD, KBD, WAD, WBD
24217856

1996
C/K Truck

G Van
5.7L

(L31)
4L60-E

(M30)
CHD, CJD, KCD, CMD, CUD, KPD, YDD, FFD, WCD, WHD
24217857

1996
F Car

Y Car
5.7L

(LT1)
4L60-E

(M30)
FFD, YDD
24217857

1996
D Car
5.7L

(L31)
4L60-E

(M30)
AHD
24217857

1996
S/T Truck

M/L Van
4.3L

(L35)
4L60-E

(M30)
TBD, TAD, MSD, MDD
24217860

1996
C/K Truck

G Van
4.3L

(L35)
4L60-E

(M30)
CAD, CBD, KAD
24217861

1996
S/T Truck
4.3L

(LF6)
4L60-E

(M30)
SHD, TLD
24217862

1996
B Car
4.3L

(L99)
4L60-E

(M30)
BBD, BCD
24217863

1996
B Car

(Includes Police Pkg.)
5.7L

(LT1)
4L60-E

(M30)
BFD, BWD, BKD
24217864

1996
F Car
3.8L

(L36)
4L60-E

(M30)
FCD, FBD
24217865

1997
S Truck
2.2L

(LN2)
4L60-E

(M30)
SAD
24217866

1997
C/K Truck

G Van
4.3L

(L35)
4L60-E

(M30)
CAD, CBD, KAD
24217867

1997
S/T Truck

M/L Van
4.3L

(L35)

4.3L

(LF6)
4L60-E

(M30)
SHD, TLD, TBD, TAD, MSD, MDD
24217868

Since you replaced the valve body, I would not suspect the above applies, it is just for your reference.

#99-07-30-005: Info - Component Slipping/DTC P1870 - Diagnosis - (Mar 18, 1999)

Subject: Component Slipping/DTC P1870 - Diagnosis

Models: 1996 Buick Roadmaster

1996 Cadillac Fleetwood

1999 Cadillac Escalade

1996-99 Chevrolet Camaro, Corvette

1996-99 Pontiac Firebird

1996-99 Chevrolet and GMC C/K, M/L, S/T, G Models

1996-99 Oldsmobile Bravada

1996-99 Holden Commodore

with Hydra-matic 4L60-E (RPO M30)

Description
Many technicians experience difficulty when diagnosing 1996-1999 4L60-E transmissions with a DTC P1870 (Transmission Component Slipping).

The purpose of this bulletin is to provide assistance for technicians that have already completed the DTC P1870 diagnostic table in the Service Manual. This bulletin will provide a diagnostic strategy for solving DTC P1870 concerns as well as give some of the most common causes for a DTC P1870.

General Information
Important: • Chevrolet Camaro, Pontiac Firebird with 3.8L V6 Engine experiencing a slip condition at 70-90 km/h (45-55 mph) when the TCC applies should refer to Corporate Service Bulletin 77-71-70A for calibration re-flash.

• 1996 Chevrolet and GMC C/K, M/L, S/T, G Models, and 1996 Oldsmobile Bravada with VCM and 4L60-E (RPO M30) with a slip or flare on the 1-2 and/or 2-3 upshift, or no 3rd or 4th gear, or launch shudder should refer to Corporate Service Bulletin 66-71-03A to ensure that a poor internal ground in the VCM does not exist.

• A DTC P1870 indicates that a mechanical malfunction exists. If any other DTC's set along with a DTC P1870, then diagnose those first. A DTC P1860 (TCC PWM Solenoid Circuit Electrical) will set if a TCC PWM solenoid circuit failure exists. A DTC P0740 (TCC Enable Solenoid Circuit Electrical) will set if a TCC enable solenoid circuit failure exists.

• When attempting to duplicate DTC P1870, it is critical that a normal operating temperature of 82 °C (180 °F) to 93 °C (200 °F) be reached. It may be difficult to attain the transmission temperature required to adequately cause the DTC to duplicate. Allow the vehicle to idle to assist in warming the powertrain.

• Optimum speed to duplicate the DTC P1870 is between 89 km/h (55 mph) and 107 km/h (63 mph).

• Commanding the TCC ON and OFF several times with the Tech II is critical to monitoring slip when sticky valves in the valve body are suspect.

• If the customer brought in the vehicle for a temporary harsh 1-2 shift and no driveability concerns are seen during a test drive, then remember that a harsh 1-2 is a result of the PCM commanding maximum line pressure from recognizing a DTC P1870.

• The PCM must recognize that a DTC P1870 has set in two consecutive key cycles to illuminate the MIL. If a DTC P1870 is not recognized on a second key cycle, then normal line pressure returns.

• Vehicles should be inspected for correct tire size, axle ratio, or calibration.

Diagnostic Approach
Action
Yes
No

Attempt to duplicate DTC P1870.

Did you duplicate DTC P1870?
Go to Slip Check Procedure
Go to TCC System Symptom Table

Slip Check Procedure
This procedure will assist in isolating what area of the transmission is causing your slip, either the TCC system or internal transmission components. After you have isolated the origin of the slip, then utilize the TCC System Symptom Table or the Internal Transmission Symptom Table of this bulletin for most common concerns.

To check for a TCC system concern
TCC slip can occur either hot or cold or in both conditions. First, perform the following test at cold transmission temperatures, then perform the same test at normal operating temperature. Ideal slip from the transmission with the TCC applied is 50 RPM or less under light to normal throttle, no heavy engine load or hard accelerating conditions.

Use the Tech II scan tool to monitor TCC slip while driving the vehicle in 4th gear at steady speed with the TCC commanded ON.
When the TCC is applied or released (release the TCC with brake pedal, not the scan tool - release the TCC by lightly applying the brake pedal while simultaneously maintaining a steady throttle position), the slip speed should drop or rise 150-300 RPM. If the slip speed does not drop, then the DTC P1870 is being caused by the torque converter system.
Action
Yes
No

Did TCC slip speed drop (150-300)?
Continue Slip Check Procedure for an internal trans concern
Go to TCC System Symptom Table

To check for an internal transmission concern
Slip should be checked in every gear to isolate in which gear the slip may be occurring. Drive the vehicle in each forward gear range D1, D2, D3 and D4. Command the TCC ON with the Tech II in each gear and monitor slip speed.

Important: Vehicle speed must be over 11 km/h (7 mph). Some TCC slip is normal when the TCC applies directly after 11 km/h (7 mph) is reached.

If the slip speed remains constant from gear to gear, then the condition is most likely TCC related. Example: Slip speed is higher in second and fourth gear than in third gear. This would lead a technician to a possible slipping band.

Action
Yes
No

Is slip speed equal in all gears?
Go to TCC System Symptom Table
Go to Internal Transmission Symptom Table

Important: These symptom tables are to be used when the following symptoms are associated with a DTC P1870.

TCC System Symptom Table Symptom
Causes

TCC SLIP (100 RPM SLIP)
• Check for bronze bushing material in the pan and filter. If bronze material is present, then the stator bushings (234) and turbine shaft (241) should be replaced (Bronze bushing may turn black with an acrid odor).

• The turbine shaft and housing (621) should be replaced if damaged.

• In rare instances, it may be necessary to check for an overheated torque converter (24) (Blue and/or distorted converter).

• TCC solenoid (66) - Perform leak check.

• Converter clutch valve (224) in pump should be checked for 13 mm (0.500 in) of bore travel without binding.

• Turbine shaft O-ring seal (618) cut.

• Turbine shaft hole not drilled to full depth. This concern can be checked by squirting trans fluid through the turbine shaft hole to check for full flow. This is a low mileage failure.

NO TCC APPLY (300 RPM SLIP)
• Converter clutch valve (224) stuck closed (Check for debris in valve bore).

• TCC PWM solenoid (396) broken/cracked. Visually inspect solenoid.

• TCC solenoid (66). Perform leak test.

• Turbine shaft O-ring seal (618) omitted.

TCC SLIP WITH STALL STUMBLE
Converter clutch valve (224) stuck open (TCC is applying).

INTERMITTENT TCC, OK COLD, SLIPS HOT
• TCC PWM solenoid (396). Leak test solenoid.

• The TCC regulator apply valve (380) and/or converter clutch shift valve (224) may be sticking/side-loading. It is possible there will not be any damage to the valve upon inspection. Transmissions produced after 2/1/98 will have a groove cut into the spring end of the regulator apply valve. This design is to help float the valve in its bore (replace valve body assembly).

Internal Transmission Symptom Table Symptom
Causes

3RD OR 4TH GEAR SLIP
• 3-2 downshift solenoid (394) ball seat retention failed. Leak test solenoid. Usually associated with a 3-4 clutch/band worn.

• 3rd accumulator retainer and ball assembly (40) leaks. Test for proper check ball operation. Usually associated with burned 3-4 clutch.

NO 4TH OR SLIPPING 4TH
• Check ball in the wrong location or extra check ball that has dropped behind the spacer plate during trans assembly. The extra check ball can block the 4th apply servo feed.

• Clutch orifice cup plug (238) not fully pressed in.

SLIP/FLARE IN ANY GEAR
Pump slide inner spring (207) or outer spring (206) omitted causing a slow slide response.

NO 3RD
Clutch orifice cup plug (238) blown out.

HARSH 1-2 UPSHIFT
4-3 sequence valve (383) stuck in bore by sediment.

NO 2-3 UPSHIFT
2-3 shift valve (368) or 2-3 shuttle valve (369) stuck in bore by sediment.

NO 3-4 UPSHIFT
3-4 shift valve (385) stuck in bore by sediment.

DTC P1870 Transmission Component Slipping
Table 1: DTC P1870 Transmission Slipping Component

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 VCM 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 +20 RPM.

When the VCM 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 DTCs P0122 or P0123

• No VSS Assy. DTC P0502

• No TFT Sensor DTCs P0712 or P0713

• No TCC Sol. Valve DTC P0740

• No 1-2 SS Valve DTCs P0751 or P0753

• No 2-3 SS Valve DTCs P0756 or P0758

• No TFP Val. Position Sw. DTC P1810

• No TCC PWM Sol. Valve DTC P1860

• The engine speed is greater than 450 RPM for 8 seconds.

• Not in fuel cutoff

• The engine torque is 50-450 lb ft.

• The gear range is D4.

• Not in 1st gear

• The TP angle is 9-35%.

• The TFT is 20-130 °C (68-266 °F).

• The TCC is ON for 5 seconds.

• The TCC is at maximum apply for 5 seconds.

• The TCC slip speed is greater than 130 RPM.

• All conditions met for 7 seconds

Action Taken When the DTC Sets
• The VCM inhibits TCC engagement.

• The VCM commands maximum line pressure.

• The VCM inhibits 4th gear if the transmission is in hot mode.

• The VCM freezes shift adapts from being updated.

• The VCM illuminates the Malfunction Indicator Lamp (MIL).

Conditions for Clearing the MIL/DTC
• The VCM turns OFF the MIL after three consecutive ignition cycles without a failure reported.

• A scan tool can clear the DTC from the VCM history. The VCM clears the DTC from the VCM history if the vehicle completes 40 warm-up cycles without a failure reported.

• The VCM cancels the DTC default actions when the fault no longer exists and the ignition is OFF long enough in order to power down the VCM.

Diagnostic Aids
• Internal transmission failures could set a DTC P1870.

• A TFP Valve Position Switch malfunction could set a DTC P1870.

Test Description
The numbers below refer to the Step numbers on the diagnostic table.

This step tests the torque converter for slippage while in a commanded lock-up state.

DTC P1870 Transmission Slipping Component Step
Action
Value(s)
Yes
No

1
Was the Powertrain On-Board Diagnostic (OBD) System Check performed?
--
Go to Step 2
Go to Powertrain On Board Diagnostic (OBD) System Check

2
Perform the transmission fluid checking procedure.

Refer to Transmission Fluid Check.

Did you perform the fluid checking procedure?
--
Go to Step 3
Go to Transmission Fluid Check

3
Install the scan tool (tech 1) ®.
Turn ON the ignition, with the engine OFF.
Important: Before clearing the DTCs, use the scan tool in order to record the Freeze Frame and Failure Records. Using the Clear Info function erases the Freeze Frame and Failure Records from the PCM.

Record the Freeze Frame and Failure Records.
Clear the DTCs.
With the engine idling and at normal operating temperature, apply the brake pedal.
Select each transmission range: D1, D2, D3, D4, N, R and P.
Refer to Transmission Fluid Pressure (TFP) Manual Valve Position Switch Logic.

Does each selected transmission range match the scan tool TFP switch A/B/C display?
--
Go to Step 4
Go to Transmission Fluid Pressure Manual Valve Position Switch Resistance Check

4
Install the Scan Tool ®.
With the engine OFF, turn the ignition switch to the RUN position.
Important: Before clearing the DTCs, use the scan tool in order to record the Freeze Frame and Failure Records for reference. The Clear Info function will erase the data.

Record the DTC Freeze Frame and Failure Records.
Drive the vehicle in 4th gear with the TCC engaged.
Is the TCC Slip Speed greater than the specified value for 7 seconds?
130 RPM
Go to Step 5
Go to Diagnostic Aids

5
Inspect the Torque Converter Clutch Solenoid Valve (TCC Sol. Valve) for the following problems: • Internal malfunction (such as sediment or damage)

• Damaged seals

Inspect the Torque Converter Clutch Pulse Width Modulation Solenoid Valve (TCC PWM Sol. Valve) for the following problems: • Internal malfunction (such as sediment or damage)

• Damaged seals

Did you find a problem?
--
Go to Step 14
Go to Step 6

6
Inspect the 1-2 Shift Solenoid Valve (1-2 SS Valve) for the following problems: • Internal malfunction (such as sediment or damage)

• Damaged seals

Inspect the 2-3 Shift Solenoid Valve (2-3 SS Valve) for the following problems: • Internal malfunction (such as sediment or damage)

• Damaged seals

Did you find a problem?
--
Go to Step 14
Go to Step 7

7
Inspect the valve body assembly for a stuck TCC signal valve.

Refer to Transmission Overhaul, in Unit Repair.

Did you find a problem?
--
Go to Step 14
Go to Step 8

8
Inspect the torque converter assembly for the following problems: • Stator roller clutch not holding

• Internal damage

Did you find a problem?
--
Go to Step 14
Go to Step 9

9
Inspect the oil pump assembly for the following problems: • A stuck converter clutch valve

• The converter clutch valve is assembled backwards

• A mispositioned converter clutch valve retaining ring

• A mispositioned pump to case gasket

• Restricted orifice cup plugs

• Damaged orifice cup plugs

• Over-tightened, or unevenly tightened pump body to cover bolts

Refer to Transmission Overhaul, in Unit Repair.

Did you find a problem?
--
Go to Step 14
Go to Step 10

10
Inspect the input housing and shaft assembly for the following problems: • Cut turbine shaft O-ring seal

• Damaged turbine shaft O-ring seal

• Restricted turbine shaft retainer and ball assembly

• Damaged turbine shaft retainer and ball assembly

Refer to Transmission Overhaul, in Unit Repair.

Did you find a problem?
--
Go to Step 14
Go to Step 11

11
Inspect the 2-4 band assembly for the following problems: • Worn 2-4 band

• Damaged 2-4 band

• Mispositioned 2-4 band

• Misassembled 2-4 band

• The band anchor pin is not engaged.

• Restricted apply passages in the 2-4 servo assembly

• Blocked apply passages in the 2-4 servo assembly

• Nicks or burrs on the servo pin

• Nicks or burrs on the pin bore in the case

• Damaged fourth servo piston

• Misassembled fourth servo piston

• Damaged band apply pin

• Incorrect band apply pin

• Damaged servo bore in the case

• Missing piston seals

• Cut piston seals

• Damaged piston seals

• Porosity in the pistons

• Porosity in the cover

• Porosity in the case

• Damaged piston seal grooves

• Plugged orifice cup plug

• Missing orifice cup plug

Refer to Transmission Overhaul, in Unit Repair.

Did you find a problem?
--
Go to Step 14
Go to Step 12

12
Inspect the forward clutch assembly for the following problems: • Worn clutch plates

• Porosity in the forward clutch piston

• Damaged forward clutch piston

• Missing forward clutch piston inner and outer seals

• Cut forward clutch piston inner and outer seals

• Damaged forward clutch piston inner and outer seals

• Missing input housing to forward clutch housing O-ring seal

• Cut input housing to forward clutch housing O-ring seal

• Damaged input housing to forward clutch housing O-ring seal

• Damaged forward clutch housing

• Damaged forward clutch housing retainer and ball assembly

• Forward clutch housing retainer and ball assembly is not sealing.

Refer to Transmission Overhaul, in Unit Repair.

Did you find a problem?
--
Go to Step 14
Go to Step 13

13
Inspect the 3-4 clutch assembly for the following problems: • Worn clutch plates

• Porosity in the 3-4 clutch piston

• Damaged 3-4 clutch piston

• Missing 3-4 clutch inner and outer seals

• Cut 3-4 clutch inner and outer seals

• Damaged 3-4 clutch inner and outer seals

• Damaged 3-4 clutch spring assembly

• Damaged 3-4 clutch apply ring

• Damaged piston seal grooves

• Plugged orifice cup plug

• Missing orifice cup plug

Refer to Transmission Overhaul, in Unit Repair.

Did you find a problem?
--
Go to Step 14
Go to Diagnostic Aids

14
In order to verify your repair, perform the following procedure: Select DTC.
Select Clear Info.
Operate the vehicle under the following conditions: • Drive the vehicle in D4, with the TCC ON, and a throttle position of 9-35%.

• Ensure that the TCC Slip Speed is -20 to +20 RPM for at least 12 seconds.

Select Specific DTC. Enter DTC P1870.
Has the test run and passed?
--
System OK
Begin

Factoryjack
Oct 28, 2010.